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	$40.38	11.865%	$45.1711	$45.17	$45.15	$45.20
Purchase #2	$128.29	5.763%	$135.6834	$135.68	$135.70	$135.70
Purchase #3	$178.32	11.182%	$198.2597	$198.26	$198.25	$198.30
Purchase #4	$168.44	13.617%	$191.3765	$191.38	$191.40	$191.40
Purchase #5	$50.38	7.855%	$54.3373	$54.34	$54.35	$54.30
Purchase #6	$86.69	11.150%	$96.3559	$96.36	$96.35	$96.40
Purchase #7	$38.91	11.205%	$43.2699	$43.27	$43.25	$43.30
7 purchase totals =	$691.41		$764.4538	$764.46	$764.45	$764.60