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	$168.51	12.791%	$190.0641	$190.06	$190.05	$190.10
Purchase #2	$221.66	10.763%	$245.5173	$245.52	$245.50	$245.50
Purchase #3	$191.74	4.790%	$200.9243	$200.92	$200.90	$200.90
Purchase #4	$43.53	13.551%	$49.4288	$49.43	$49.45	$49.40
Purchase #5	$184.76	3.686%	$191.5703	$191.57	$191.55	$191.60
Purchase #6	$209.54	3.266%	$216.3836	$216.38	$216.40	$216.40
Purchase #7	$176.68	6.791%	$188.6783	$188.68	$188.70	$188.70
7 purchase totals =	$1,196.42		$1,282.5667	$1,282.56	$1,282.55	$1,282.60