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	$125.41	5.222%	$131.9589	$131.96	$131.95	$132.00
Purchase #2	$118.96	7.107%	$127.4145	$127.41	$127.40	$127.40
Purchase #3	$101.31	5.675%	$107.0593	$107.06	$107.05	$107.10
Purchase #4	$227.73	7.802%	$245.4975	$245.50	$245.50	$245.50
Purchase #5	$177.92	12.874%	$200.8254	$200.83	$200.85	$200.80
Purchase #6	$26.51	4.645%	$27.7414	$27.74	$27.75	$27.70
Purchase #7	$237.33	7.184%	$254.3798	$254.38	$254.40	$254.40
7 purchase totals =	$1,015.17		$1,094.8768	$1,094.88	$1,094.90	$1,094.90