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	$145.94	13.822%	$166.1118	$166.11	$166.10	$166.10
Purchase #2	$113.62	8.338%	$123.0936	$123.09	$123.10	$123.10
Purchase #3	$115.58	9.253%	$126.2746	$126.27	$126.25	$126.30
Purchase #4	$91.71	3.336%	$94.7694	$94.77	$94.75	$94.80
Purchase #5	$54.41	9.143%	$59.3847	$59.38	$59.40	$59.40
Purchase #6	$170.67	11.722%	$190.6759	$190.68	$190.70	$190.70
Purchase #7	$165.33	5.582%	$174.5587	$174.56	$174.55	$174.60
7 purchase totals =	$857.26		$934.8687	$934.86	$934.85	$935.00