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	$98.73	6.763%	$105.4071	$105.41	$105.40	$105.40
Purchase #2	$223.67	9.823%	$245.6411	$245.64	$245.65	$245.60
Purchase #3	$43.29	11.615%	$48.3181	$48.32	$48.30	$48.30
Purchase #4	$213.81	9.346%	$233.7927	$233.79	$233.80	$233.80
Purchase #5	$99.48	5.363%	$104.8151	$104.82	$104.80	$104.80
Purchase #6	$50.26	5.171%	$52.8589	$52.86	$52.85	$52.90
Purchase #7	$106.62	3.607%	$110.4658	$110.47	$110.45	$110.50
7 purchase totals =	$835.86		$901.2988	$901.31	$901.25	$901.30