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	$211.73	6.208%	$224.8742	$224.87	$224.85	$224.90
Purchase #2	$89.28	11.731%	$99.7534	$99.75	$99.75	$99.80
Purchase #3	$171.40	9.109%	$187.0128	$187.01	$187.00	$187.00
Purchase #4	$99.83	9.311%	$109.1252	$109.13	$109.15	$109.10
Purchase #5	$163.93	9.323%	$179.2132	$179.21	$179.20	$179.20
Purchase #6	$171.65	13.573%	$194.9481	$194.95	$194.95	$194.90
Purchase #7	$23.39	3.292%	$24.16	$24.16	$24.15	$24.20
7 purchase totals =	$931.21		$1,019.0869	$1,019.08	$1,019.05	$1,019.10