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	$156.82	7.869%	$169.1602	$169.16	$169.15	$169.20
Purchase #2	$147.74	7.257%	$158.4615	$158.46	$158.45	$158.50
Purchase #3	$198.41	10.753%	$219.745	$219.75	$219.75	$219.70
Purchase #4	$129.93	11.681%	$145.1071	$145.11	$145.10	$145.10
Purchase #5	$166.69	3.716%	$172.8842	$172.88	$172.90	$172.90
Purchase #6	$204.26	11.331%	$227.4047	$227.40	$227.40	$227.40
Purchase #7	$85.26	4.723%	$89.2868	$89.29	$89.30	$89.30
7 purchase totals =	$1,089.11		$1,182.0495	$1,182.05	$1,182.05	$1,182.10