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	$29.37	12.700%	$33.1	$33.10	$33.10	$33.10
Purchase #2	$175.57	11.477%	$195.7202	$195.72	$195.70	$195.70
Purchase #3	$127.25	10.553%	$140.6787	$140.68	$140.70	$140.70
Purchase #4	$96.52	7.376%	$103.6393	$103.64	$103.65	$103.60
Purchase #5	$36.71	3.179%	$37.877	$37.88	$37.90	$37.90
Purchase #6	$120.82	6.738%	$128.9609	$128.96	$128.95	$129.00
Purchase #7	$10.65	11.262%	$11.8494	$11.85	$11.85	$11.80
7 purchase totals =	$596.89		$651.8255	$651.83	$651.85	$651.80