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	$119.80	4.218%	$124.8532	$124.85	$124.85	$124.90
Purchase #2	$151.84	9.543%	$166.3301	$166.33	$166.35	$166.30
Purchase #3	$87.58	5.392%	$92.3023	$92.30	$92.30	$92.30
Purchase #4	$24.49	4.109%	$25.4963	$25.50	$25.50	$25.50
Purchase #5	$69.38	6.555%	$73.9279	$73.93	$73.95	$73.90
Purchase #6	$213.61	4.820%	$223.906	$223.91	$223.90	$223.90
Purchase #7	$35.41	5.352%	$37.3051	$37.31	$37.30	$37.30
7 purchase totals =	$702.11		$744.1209	$744.13	$744.15	$744.10