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	$179.52	3.612%	$186.0043	$186.00	$186.00	$186.00
Purchase #2	$31.36	10.801%	$34.7472	$34.75	$34.75	$34.70
Purchase #3	$63.42	3.840%	$65.8553	$65.86	$65.85	$65.90
Purchase #4	$92.90	6.873%	$99.285	$99.29	$99.30	$99.30
Purchase #5	$120.62	5.388%	$127.119	$127.12	$127.10	$127.10
Purchase #6	$141.73	11.779%	$158.4244	$158.42	$158.40	$158.40
Purchase #7	$196.67	13.490%	$223.2008	$223.20	$223.20	$223.20
7 purchase totals =	$826.22		$894.6360	$894.64	$894.60	$894.60