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	$112.53	13.750%	$128.0029	$128.00	$128.00	$128.00
Purchase #2	$128.83	4.323%	$134.3993	$134.40	$134.40	$134.40
Purchase #3	$147.76	6.315%	$157.091	$157.09	$157.10	$157.10
Purchase #4	$44.48	3.104%	$45.8607	$45.86	$45.85	$45.90
Purchase #5	$149.38	10.640%	$165.274	$165.27	$165.25	$165.30
Purchase #6	$142.61	5.753%	$150.8144	$150.81	$150.80	$150.80
Purchase #7	$10.33	6.121%	$10.9623	$10.96	$10.95	$11.00
7 purchase totals =	$735.92		$792.4046	$792.39	$792.35	$792.50