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	$94.76	12.270%	$106.3871	$106.39	$106.40	$106.40
Purchase #2	$115.73	7.545%	$124.4618	$124.46	$124.45	$124.50
Purchase #3	$180.87	8.793%	$196.7739	$196.77	$196.75	$196.80
Purchase #4	$92.28	11.673%	$103.0518	$103.05	$103.05	$103.10
Purchase #5	$187.81	11.603%	$209.6016	$209.60	$209.60	$209.60
Purchase #6	$98.82	6.400%	$105.1445	$105.14	$105.15	$105.10
Purchase #7	$209.49	13.404%	$237.57	$237.57	$237.55	$237.60
7 purchase totals =	$979.76		$1,082.9907	$1,082.98	$1,082.95	$1,083.10