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	$171.65	11.454%	$191.3108	$191.31	$191.30	$191.30
Purchase #2	$226.57	5.103%	$238.1319	$238.13	$238.15	$238.10
Purchase #3	$244.44	12.545%	$275.105	$275.11	$275.10	$275.10
Purchase #4	$44.25	11.193%	$49.2029	$49.20	$49.20	$49.20
Purchase #5	$76.93	12.260%	$86.3616	$86.36	$86.35	$86.40
Purchase #6	$116.49	5.673%	$123.0985	$123.10	$123.10	$123.10
Purchase #7	$51.61	4.748%	$54.0604	$54.06	$54.05	$54.10
7 purchase totals =	$931.94		$1,017.2711	$1,017.27	$1,017.25	$1,017.30