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	$151.85	6.786%	$162.1545	$162.15	$162.15	$162.20
Purchase #2	$199.77	3.559%	$206.8798	$206.88	$206.90	$206.90
Purchase #3	$98.32	3.238%	$101.5036	$101.50	$101.50	$101.50
Purchase #4	$214.61	13.119%	$242.7647	$242.76	$242.75	$242.80
Purchase #5	$80.69	10.869%	$89.4602	$89.46	$89.45	$89.50
Purchase #6	$223.53	5.318%	$235.4173	$235.42	$235.40	$235.40
Purchase #7	$59.58	9.531%	$65.2586	$65.26	$65.25	$65.30
7 purchase totals =	$1,028.35		$1,103.4387	$1,103.43	$1,103.40	$1,103.60