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	$103.65	10.866%	$114.9126	$114.91	$114.90	$114.90
Purchase #2	$62.76	11.397%	$69.9128	$69.91	$69.90	$69.90
Purchase #3	$200.91	13.623%	$228.28	$228.28	$228.30	$228.30
Purchase #4	$93.90	8.311%	$101.704	$101.70	$101.70	$101.70
Purchase #5	$199.66	11.118%	$221.8582	$221.86	$221.85	$221.90
Purchase #6	$165.52	13.773%	$188.3171	$188.32	$188.30	$188.30
Purchase #7	$90.32	10.586%	$99.8813	$99.88	$99.90	$99.90
7 purchase totals =	$916.72		$1,024.8660	$1,024.86	$1,024.85	$1,024.90