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	$93.77	12.413%	$105.4097	$105.41	$105.40	$105.40
Purchase #2	$33.97	4.419%	$35.4711	$35.47	$35.45	$35.50
Purchase #3	$60.55	6.123%	$64.2575	$64.26	$64.25	$64.30
Purchase #4	$223.27	4.840%	$234.0763	$234.08	$234.10	$234.10
Purchase #5	$58.63	12.230%	$65.8004	$65.80	$65.80	$65.80
Purchase #6	$49.59	12.364%	$55.7213	$55.72	$55.70	$55.70
Purchase #7	$38.89	11.281%	$43.2772	$43.28	$43.30	$43.30
7 purchase totals =	$558.67		$604.0135	$604.02	$604.00	$604.10