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	$222.62	8.864%	$242.353	$242.35	$242.35	$242.40
Purchase #2	$139.67	10.301%	$154.0574	$154.06	$154.05	$154.10
Purchase #3	$42.78	10.322%	$47.1958	$47.20	$47.20	$47.20
Purchase #4	$100.85	10.711%	$111.652	$111.65	$111.65	$111.70
Purchase #5	$87.61	13.121%	$99.1053	$99.11	$99.10	$99.10
Purchase #6	$79.66	7.847%	$85.9109	$85.91	$85.90	$85.90
Purchase #7	$109.32	3.746%	$113.4151	$113.42	$113.40	$113.40
7 purchase totals =	$782.51		$853.6895	$853.70	$853.65	$853.80