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	$167.35	8.700%	$181.9095	$181.91	$181.90	$181.90
Purchase #2	$159.86	5.684%	$168.9464	$168.95	$168.95	$168.90
Purchase #3	$49.33	11.610%	$55.0572	$55.06	$55.05	$55.10
Purchase #4	$77.55	10.110%	$85.3903	$85.39	$85.40	$85.40
Purchase #5	$147.45	12.641%	$166.0892	$166.09	$166.10	$166.10
Purchase #6	$229.36	5.568%	$242.1308	$242.13	$242.15	$242.10
Purchase #7	$178.44	5.251%	$187.8099	$187.81	$187.80	$187.80
7 purchase totals =	$1,009.34		$1,087.3333	$1,087.34	$1,087.35	$1,087.30