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	$165.62	12.396%	$186.1503	$186.15	$186.15	$186.20
Purchase #2	$68.92	6.133%	$73.1469	$73.15	$73.15	$73.10
Purchase #3	$157.68	8.743%	$171.466	$171.47	$171.45	$171.50
Purchase #4	$151.33	10.426%	$167.1077	$167.11	$167.10	$167.10
Purchase #5	$90.32	10.185%	$99.5191	$99.52	$99.50	$99.50
Purchase #6	$218.37	4.519%	$228.2381	$228.24	$228.25	$228.20
Purchase #7	$200.35	4.457%	$209.2796	$209.28	$209.30	$209.30
7 purchase totals =	$1,052.59		$1,134.9077	$1,134.92	$1,134.90	$1,134.90