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	$118.69	7.323%	$127.3817	$127.38	$127.40	$127.40
Purchase #2	$100.94	7.320%	$108.3288	$108.33	$108.35	$108.30
Purchase #3	$7.59	6.420%	$8.0773	$8.08	$8.10	$8.10
Purchase #4	$111.72	7.518%	$120.1191	$120.12	$120.10	$120.10
Purchase #5	$160.25	12.774%	$180.7203	$180.72	$180.70	$180.70
Purchase #6	$47.94	11.590%	$53.4962	$53.50	$53.50	$53.50
Purchase #7	$70.43	12.170%	$79.0013	$79.00	$79.00	$79.00
7 purchase totals =	$617.56		$677.1247	$677.13	$677.15	$677.10