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	$179.30	4.425%	$187.234	$187.23	$187.25	$187.20
Purchase #2	$127.53	13.361%	$144.5693	$144.57	$144.55	$144.60
Purchase #3	$104.34	6.406%	$111.024	$111.02	$111.00	$111.00
Purchase #4	$233.25	5.674%	$246.4846	$246.48	$246.50	$246.50
Purchase #5	$134.31	7.428%	$144.2865	$144.29	$144.30	$144.30
Purchase #6	$229.41	3.818%	$238.1689	$238.17	$238.15	$238.20
Purchase #7	$49.56	13.818%	$56.4082	$56.41	$56.40	$56.40
7 purchase totals =	$1,057.70		$1,128.1755	$1,128.17	$1,128.15	$1,128.20