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	$172.62	3.673%	$178.9603	$178.96	$178.95	$179.00
Purchase #2	$249.85	9.148%	$272.7063	$272.71	$272.70	$272.70
Purchase #3	$100.36	9.131%	$109.5239	$109.52	$109.50	$109.50
Purchase #4	$245.50	9.740%	$269.4117	$269.41	$269.40	$269.40
Purchase #5	$64.98	5.536%	$68.5773	$68.58	$68.60	$68.60
Purchase #6	$82.46	8.553%	$89.5128	$89.51	$89.50	$89.50
Purchase #7	$161.53	6.288%	$171.687	$171.69	$171.70	$171.70
7 purchase totals =	$1,077.30		$1,160.3793	$1,160.38	$1,160.35	$1,160.40