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	$188.85	4.514%	$197.3747	$197.37	$197.35	$197.40
Purchase #2	$181.63	4.140%	$189.1495	$189.15	$189.15	$189.10
Purchase #3	$124.72	3.339%	$128.8844	$128.88	$128.90	$128.90
Purchase #4	$174.62	11.111%	$194.022	$194.02	$194.00	$194.00
Purchase #5	$86.32	3.541%	$89.3766	$89.38	$89.40	$89.40
Purchase #6	$118.44	5.281%	$124.6948	$124.69	$124.70	$124.70
Purchase #7	$20.56	5.508%	$21.6924	$21.69	$21.70	$21.70
7 purchase totals =	$895.14		$945.1944	$945.18	$945.20	$945.20