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	$171.86	11.571%	$191.7459	$191.75	$191.75	$191.70
Purchase #2	$56.33	3.870%	$58.51	$58.51	$58.50	$58.50
Purchase #3	$183.83	6.796%	$196.3231	$196.32	$196.30	$196.30
Purchase #4	$229.97	9.377%	$251.5343	$251.53	$251.55	$251.50
Purchase #5	$137.87	7.647%	$148.4129	$148.41	$148.40	$148.40
Purchase #6	$19.61	11.203%	$21.8069	$21.81	$21.80	$21.80
Purchase #7	$111.72	3.118%	$115.2034	$115.20	$115.20	$115.20
7 purchase totals =	$911.19		$983.5365	$983.53	$983.50	$983.40