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	$56.55	3.489%	$58.523	$58.52	$58.50	$58.50
Purchase #2	$26.36	3.601%	$27.3092	$27.31	$27.30	$27.30
Purchase #3	$116.69	8.218%	$126.2796	$126.28	$126.30	$126.30
Purchase #4	$66.51	9.223%	$72.6442	$72.64	$72.65	$72.60
Purchase #5	$147.50	9.108%	$160.9343	$160.93	$160.95	$160.90
Purchase #6	$89.31	9.550%	$97.8391	$97.84	$97.85	$97.80
Purchase #7	$31.50	6.425%	$33.5239	$33.52	$33.50	$33.50
7 purchase totals =	$534.42		$577.0533	$577.04	$577.05	$576.90