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	$46.25	12.666%	$52.108	$52.11	$52.10	$52.10
Purchase #2	$41.37	7.118%	$44.3147	$44.31	$44.30	$44.30
Purchase #3	$128.46	6.623%	$136.9679	$136.97	$136.95	$137.00
Purchase #4	$37.88	7.472%	$40.7104	$40.71	$40.70	$40.70
Purchase #5	$79.36	7.390%	$85.2247	$85.22	$85.20	$85.20
Purchase #6	$78.41	9.118%	$85.5594	$85.56	$85.55	$85.60
Purchase #7	$68.99	4.822%	$72.3167	$72.32	$72.30	$72.30
7 purchase totals =	$480.72		$517.2018	$517.20	$517.10	$517.20