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	$136.90	6.844%	$146.2694	$146.27	$146.25	$146.30
Purchase #2	$84.84	4.779%	$88.8945	$88.89	$88.90	$88.90
Purchase #3	$38.75	6.798%	$41.3842	$41.38	$41.40	$41.40
Purchase #4	$200.28	11.690%	$223.6927	$223.69	$223.70	$223.70
Purchase #5	$150.74	5.431%	$158.9267	$158.93	$158.95	$158.90
Purchase #6	$210.97	8.459%	$228.816	$228.82	$228.80	$228.80
Purchase #7	$158.69	4.495%	$165.8231	$165.82	$165.80	$165.80
7 purchase totals =	$981.17		$1,053.8066	$1,053.80	$1,053.80	$1,053.80