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	$91.42	7.457%	$98.2372	$98.24	$98.25	$98.20
Purchase #2	$49.87	9.756%	$54.7353	$54.74	$54.75	$54.70
Purchase #3	$231.96	4.435%	$242.2474	$242.25	$242.25	$242.20
Purchase #4	$217.90	9.563%	$238.7378	$238.74	$238.75	$238.70
Purchase #5	$182.90	9.740%	$200.7145	$200.71	$200.70	$200.70
Purchase #6	$98.82	13.642%	$112.301	$112.30	$112.30	$112.30
Purchase #7	$243.31	13.803%	$276.8941	$276.89	$276.90	$276.90
7 purchase totals =	$1,116.18		$1,223.8673	$1,223.87	$1,223.90	$1,223.70