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	$174.41	12.649%	$196.4711	$196.47	$196.45	$196.50
Purchase #2	$72.41	7.616%	$77.9247	$77.92	$77.90	$77.90
Purchase #3	$154.77	11.269%	$172.211	$172.21	$172.20	$172.20
Purchase #4	$205.70	8.566%	$223.3203	$223.32	$223.30	$223.30
Purchase #5	$166.69	13.606%	$189.3698	$189.37	$189.35	$189.40
Purchase #6	$63.89	11.631%	$71.321	$71.32	$71.30	$71.30
Purchase #7	$78.74	10.236%	$86.7998	$86.80	$86.80	$86.80
7 purchase totals =	$916.61		$1,017.4177	$1,017.41	$1,017.30	$1,017.40