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	$67.26	10.779%	$74.51	$74.51	$74.50	$74.50
Purchase #2	$151.73	13.856%	$172.7537	$172.75	$172.75	$172.80
Purchase #3	$152.48	8.352%	$165.2151	$165.22	$165.20	$165.20
Purchase #4	$243.38	3.320%	$251.4602	$251.46	$251.45	$251.50
Purchase #5	$236.74	13.392%	$268.4442	$268.44	$268.45	$268.40
Purchase #6	$203.68	11.592%	$227.2906	$227.29	$227.30	$227.30
Purchase #7	$76.56	7.356%	$82.1918	$82.19	$82.20	$82.20
7 purchase totals =	$1,131.83		$1,241.8656	$1,241.86	$1,241.85	$1,241.90