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	$196.48	12.765%	$221.5607	$221.56	$221.55	$221.60
Purchase #2	$223.60	8.367%	$242.3086	$242.31	$242.30	$242.30
Purchase #3	$205.40	11.464%	$228.9471	$228.95	$228.95	$228.90
Purchase #4	$95.46	10.395%	$105.3831	$105.38	$105.40	$105.40
Purchase #5	$70.71	10.155%	$77.8906	$77.89	$77.90	$77.90
Purchase #6	$89.76	6.440%	$95.5405	$95.54	$95.55	$95.50
Purchase #7	$115.44	11.573%	$128.7999	$128.80	$128.80	$128.80
7 purchase totals =	$996.85		$1,100.4305	$1,100.43	$1,100.45	$1,100.40