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	$183.62	4.459%	$191.8076	$191.81	$191.80	$191.80
Purchase #2	$157.33	8.225%	$170.2704	$170.27	$170.25	$170.30
Purchase #3	$22.94	6.734%	$24.4848	$24.48	$24.50	$24.50
Purchase #4	$131.74	13.476%	$149.4933	$149.49	$149.50	$149.50
Purchase #5	$182.42	7.489%	$196.0814	$196.08	$196.10	$196.10
Purchase #6	$102.56	11.455%	$114.3082	$114.31	$114.30	$114.30
Purchase #7	$199.37	11.481%	$222.2597	$222.26	$222.25	$222.30
7 purchase totals =	$979.98		$1,068.7054	$1,068.70	$1,068.70	$1,068.80