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	$152.57	10.865%	$169.1467	$169.15	$169.15	$169.10
Purchase #2	$93.76	5.306%	$98.7349	$98.73	$98.75	$98.70
Purchase #3	$196.52	13.507%	$223.064	$223.06	$223.05	$223.10
Purchase #4	$81.79	6.491%	$87.099	$87.10	$87.10	$87.10
Purchase #5	$57.69	3.513%	$59.7166	$59.72	$59.70	$59.70
Purchase #6	$241.95	7.198%	$259.3656	$259.37	$259.35	$259.40
Purchase #7	$98.55	10.779%	$109.1727	$109.17	$109.15	$109.20
7 purchase totals =	$922.83		$1,006.2995	$1,006.30	$1,006.25	$1,006.30