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	$185.42	3.186%	$191.3275	$191.33	$191.35	$191.30
Purchase #2	$75.72	10.278%	$83.5025	$83.50	$83.50	$83.50
Purchase #3	$213.68	13.539%	$242.6101	$242.61	$242.60	$242.60
Purchase #4	$50.96	8.701%	$55.394	$55.39	$55.40	$55.40
Purchase #5	$175.99	12.257%	$197.5611	$197.56	$197.55	$197.60
Purchase #6	$147.39	3.194%	$152.0976	$152.10	$152.10	$152.10
Purchase #7	$76.46	4.813%	$80.14	$80.14	$80.15	$80.10
7 purchase totals =	$925.62		$1,002.6328	$1,002.63	$1,002.65	$1,002.60