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	$166.65	4.411%	$174.0009	$174.00	$174.00	$174.00
Purchase #2	$104.50	6.495%	$111.2873	$111.29	$111.30	$111.30
Purchase #3	$60.41	8.385%	$65.4754	$65.48	$65.50	$65.50
Purchase #4	$64.60	4.690%	$67.6297	$67.63	$67.65	$67.60
Purchase #5	$152.36	8.561%	$165.4035	$165.40	$165.40	$165.40
Purchase #6	$236.98	11.387%	$263.9649	$263.96	$263.95	$264.00
Purchase #7	$164.27	9.533%	$179.9299	$179.93	$179.95	$179.90
7 purchase totals =	$949.77		$1,027.6916	$1,027.69	$1,027.75	$1,027.70