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	$82.66	7.691%	$89.0174	$89.02	$89.00	$89.00
Purchase #2	$17.40	8.459%	$18.8719	$18.87	$18.85	$18.90
Purchase #3	$46.95	13.657%	$53.362	$53.36	$53.35	$53.40
Purchase #4	$184.54	5.181%	$194.101	$194.10	$194.10	$194.10
Purchase #5	$179.96	6.310%	$191.3155	$191.32	$191.30	$191.30
Purchase #6	$129.57	8.302%	$140.3269	$140.33	$140.35	$140.30
Purchase #7	$95.57	10.676%	$105.7731	$105.77	$105.75	$105.80
7 purchase totals =	$736.65		$792.7678	$792.77	$792.70	$792.80