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	$44.58	4.607%	$46.6338	$46.63	$46.65	$46.60
Purchase #2	$21.84	11.328%	$24.314	$24.31	$24.30	$24.30
Purchase #3	$240.89	11.574%	$268.7706	$268.77	$268.75	$268.80
Purchase #4	$124.59	5.254%	$131.136	$131.14	$131.15	$131.10
Purchase #5	$211.28	11.121%	$234.7764	$234.78	$234.80	$234.80
Purchase #6	$38.52	8.814%	$41.9152	$41.92	$41.90	$41.90
Purchase #7	$43.56	4.665%	$45.5921	$45.59	$45.60	$45.60
7 purchase totals =	$725.26		$793.1381	$793.14	$793.15	$793.10