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	$30.84	4.215%	$32.1399	$32.14	$32.15	$32.10
Purchase #2	$233.78	3.695%	$242.4182	$242.42	$242.40	$242.40
Purchase #3	$85.35	6.377%	$90.7928	$90.79	$90.80	$90.80
Purchase #4	$211.29	6.227%	$224.447	$224.45	$224.45	$224.40
Purchase #5	$202.56	6.334%	$215.3902	$215.39	$215.40	$215.40
Purchase #6	$213.84	11.406%	$238.2306	$238.23	$238.25	$238.20
Purchase #7	$99.65	12.614%	$112.2199	$112.22	$112.20	$112.20
7 purchase totals =	$1,077.31		$1,155.6386	$1,155.64	$1,155.65	$1,155.50