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	$229.76	9.185%	$250.8635	$250.86	$250.85	$250.90
Purchase #2	$231.46	9.373%	$253.1547	$253.15	$253.15	$253.20
Purchase #3	$25.48	11.347%	$28.3712	$28.37	$28.35	$28.40
Purchase #4	$168.73	8.481%	$183.04	$183.04	$183.05	$183.00
Purchase #5	$72.54	7.684%	$78.114	$78.11	$78.10	$78.10
Purchase #6	$33.87	9.250%	$37.003	$37.00	$37.00	$37.00
Purchase #7	$118.94	9.336%	$130.0442	$130.04	$130.05	$130.00
7 purchase totals =	$880.78		$960.5906	$960.57	$960.55	$960.60