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	$46.34	3.793%	$48.0977	$48.10	$48.10	$48.10
Purchase #2	$51.72	4.150%	$53.8664	$53.87	$53.85	$53.90
Purchase #3	$26.57	8.609%	$28.8574	$28.86	$28.85	$28.90
Purchase #4	$250.74	7.465%	$269.4577	$269.46	$269.45	$269.50
Purchase #5	$34.35	6.511%	$36.5865	$36.59	$36.60	$36.60
Purchase #6	$19.28	11.305%	$21.4596	$21.46	$21.45	$21.50
Purchase #7	$89.79	5.145%	$94.4097	$94.41	$94.40	$94.40
7 purchase totals =	$518.79		$552.7350	$552.75	$552.70	$552.90