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	$190.83	6.584%	$203.3942	$203.39	$203.40	$203.40
Purchase #2	$34.50	8.398%	$37.3973	$37.40	$37.40	$37.40
Purchase #3	$85.63	6.461%	$91.1626	$91.16	$91.15	$91.20
Purchase #4	$237.30	4.711%	$248.4792	$248.48	$248.50	$248.50
Purchase #5	$41.65	12.156%	$46.713	$46.71	$46.70	$46.70
Purchase #6	$73.97	9.302%	$80.8507	$80.85	$80.85	$80.90
Purchase #7	$42.91	6.290%	$45.609	$45.61	$45.60	$45.60
7 purchase totals =	$706.79		$753.6060	$753.60	$753.60	$753.70