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	$41.32	4.696%	$43.2604	$43.26	$43.25	$43.30
Purchase #2	$56.97	7.314%	$61.1368	$61.14	$61.15	$61.10
Purchase #3	$44.49	13.715%	$50.5918	$50.59	$50.60	$50.60
Purchase #4	$92.32	7.481%	$99.2265	$99.23	$99.25	$99.20
Purchase #5	$163.40	7.622%	$175.8543	$175.85	$175.85	$175.90
Purchase #6	$162.56	10.261%	$179.2403	$179.24	$179.25	$179.20
Purchase #7	$198.54	12.398%	$223.155	$223.16	$223.15	$223.20
7 purchase totals =	$759.60		$832.4651	$832.47	$832.50	$832.50