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	$93.70	5.817%	$99.1505	$99.15	$99.15	$99.20
Purchase #2	$63.76	6.165%	$67.6908	$67.69	$67.70	$67.70
Purchase #3	$180.72	8.547%	$196.1661	$196.17	$196.15	$196.20
Purchase #4	$202.98	5.590%	$214.3266	$214.33	$214.35	$214.30
Purchase #5	$237.97	3.808%	$247.0319	$247.03	$247.05	$247.00
Purchase #6	$111.43	4.107%	$116.0064	$116.01	$116.00	$116.00
Purchase #7	$107.81	4.388%	$112.5407	$112.54	$112.55	$112.50
7 purchase totals =	$998.37		$1,052.9130	$1,052.92	$1,052.95	$1,052.90