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	$88.60	10.333%	$97.755	$97.76	$97.75	$97.80
Purchase #2	$180.32	10.542%	$199.3293	$199.33	$199.35	$199.30
Purchase #3	$98.79	13.110%	$111.7414	$111.74	$111.75	$111.70
Purchase #4	$223.46	12.238%	$250.807	$250.81	$250.80	$250.80
Purchase #5	$85.44	8.472%	$92.6785	$92.68	$92.70	$92.70
Purchase #6	$162.25	4.394%	$169.3793	$169.38	$169.40	$169.40
Purchase #7	$50.51	12.430%	$56.7884	$56.79	$56.80	$56.80
7 purchase totals =	$889.37		$978.4789	$978.49	$978.55	$978.50