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	$112.71	10.222%	$124.2312	$124.23	$124.25	$124.20
Purchase #2	$118.72	10.604%	$131.3091	$131.31	$131.30	$131.30
Purchase #3	$199.85	3.200%	$206.2452	$206.25	$206.25	$206.20
Purchase #4	$220.74	9.599%	$241.9288	$241.93	$241.95	$241.90
Purchase #5	$149.95	4.305%	$156.4053	$156.41	$156.40	$156.40
Purchase #6	$74.63	12.442%	$83.9155	$83.92	$83.90	$83.90
Purchase #7	$148.82	7.416%	$159.8565	$159.86	$159.85	$159.90
7 purchase totals =	$1,025.42		$1,103.8916	$1,103.91	$1,103.90	$1,103.80