Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$185.91	4.486%	$194.2499	$194.25	$194.25	$194.20
Purchase #2	$222.70	12.371%	$250.2502	$250.25	$250.25	$250.30
Purchase #3	$162.96	5.586%	$172.0629	$172.06	$172.05	$172.10
Purchase #4	$210.59	10.368%	$232.424	$232.42	$232.40	$232.40
Purchase #5	$163.46	5.381%	$172.2558	$172.26	$172.25	$172.30
Purchase #6	$115.49	10.345%	$127.4374	$127.44	$127.45	$127.40
Purchase #7	$223.89	6.407%	$238.2346	$238.23	$238.25	$238.20
7 purchase totals =	$1,285.00		$1,386.9148	$1,386.91	$1,386.90	$1,386.90