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	$95.89	8.425%	$103.9687	$103.97	$103.95	$104.00
Purchase #2	$215.89	4.862%	$226.3866	$226.39	$226.40	$226.40
Purchase #3	$81.48	5.165%	$85.6884	$85.69	$85.70	$85.70
Purchase #4	$156.77	11.335%	$174.5399	$174.54	$174.55	$174.50
Purchase #5	$18.38	10.535%	$20.3163	$20.32	$20.30	$20.30
Purchase #6	$212.86	12.448%	$239.3568	$239.36	$239.35	$239.40
Purchase #7	$48.51	11.381%	$54.0309	$54.03	$54.05	$54.00
7 purchase totals =	$829.78		$904.2876	$904.30	$904.30	$904.30