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	$158.61	6.788%	$169.3764	$169.38	$169.40	$169.40
Purchase #2	$130.41	12.260%	$146.3983	$146.40	$146.40	$146.40
Purchase #3	$25.43	10.619%	$28.1304	$28.13	$28.15	$28.10
Purchase #4	$247.38	6.419%	$263.2593	$263.26	$263.25	$263.30
Purchase #5	$54.84	9.511%	$60.0558	$60.06	$60.05	$60.10
Purchase #6	$250.97	12.718%	$282.8884	$282.89	$282.90	$282.90
Purchase #7	$88.95	11.633%	$99.2976	$99.30	$99.30	$99.30
7 purchase totals =	$956.59		$1,049.4062	$1,049.42	$1,049.45	$1,049.50