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	$235.73	12.442%	$265.0595	$265.06	$265.05	$265.10
Purchase #2	$171.46	4.636%	$179.4089	$179.41	$179.40	$179.40
Purchase #3	$31.35	4.677%	$32.8162	$32.82	$32.80	$32.80
Purchase #4	$77.30	6.148%	$82.0524	$82.05	$82.05	$82.10
Purchase #5	$226.91	6.290%	$241.1826	$241.18	$241.20	$241.20
Purchase #6	$151.63	11.145%	$168.5292	$168.53	$168.55	$168.50
Purchase #7	$142.74	11.715%	$159.462	$159.46	$159.45	$159.50
7 purchase totals =	$1,037.12		$1,128.5108	$1,128.51	$1,128.50	$1,128.60