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	$211.96	11.348%	$236.0132	$236.01	$236.00	$236.00
Purchase #2	$62.87	7.809%	$67.7795	$67.78	$67.80	$67.80
Purchase #3	$109.58	13.540%	$124.4171	$124.42	$124.40	$124.40
Purchase #4	$223.69	3.622%	$231.7921	$231.79	$231.80	$231.80
Purchase #5	$82.44	10.327%	$90.9536	$90.95	$90.95	$91.00
Purchase #6	$133.96	6.220%	$142.2923	$142.29	$142.30	$142.30
Purchase #7	$111.34	13.390%	$126.2484	$126.25	$126.25	$126.20
7 purchase totals =	$935.84		$1,019.4962	$1,019.49	$1,019.50	$1,019.50