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	$131.98	9.421%	$144.4138	$144.41	$144.40	$144.40
Purchase #2	$64.50	11.864%	$72.1523	$72.15	$72.15	$72.20
Purchase #3	$106.74	4.873%	$111.9414	$111.94	$111.95	$111.90
Purchase #4	$33.30	6.451%	$35.4482	$35.45	$35.45	$35.40
Purchase #5	$194.29	8.659%	$211.1136	$211.11	$211.10	$211.10
Purchase #6	$88.67	11.642%	$98.993	$98.99	$99.00	$99.00
Purchase #7	$164.61	9.458%	$180.1788	$180.18	$180.20	$180.20
7 purchase totals =	$784.09		$854.2411	$854.23	$854.25	$854.20