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	$155.74	11.281%	$173.309	$173.31	$173.30	$173.30
Purchase #2	$59.30	3.220%	$61.2095	$61.21	$61.20	$61.20
Purchase #3	$53.67	10.639%	$59.38	$59.38	$59.40	$59.40
Purchase #4	$128.83	8.564%	$139.863	$139.86	$139.85	$139.90
Purchase #5	$26.38	8.506%	$28.6239	$28.62	$28.60	$28.60
Purchase #6	$167.74	3.203%	$173.1127	$173.11	$173.10	$173.10
Purchase #7	$56.36	3.705%	$58.4481	$58.45	$58.45	$58.40
7 purchase totals =	$648.02		$693.9462	$693.94	$693.90	$693.90