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	$248.31	5.853%	$262.8436	$262.84	$262.85	$262.80
Purchase #2	$42.92	12.362%	$48.2258	$48.23	$48.25	$48.20
Purchase #3	$57.95	8.237%	$62.7233	$62.72	$62.70	$62.70
Purchase #4	$26.52	5.226%	$27.9059	$27.91	$27.90	$27.90
Purchase #5	$112.66	12.681%	$126.9464	$126.95	$126.95	$126.90
Purchase #6	$171.55	9.819%	$188.3945	$188.39	$188.40	$188.40
Purchase #7	$81.27	5.234%	$85.5237	$85.52	$85.50	$85.50
7 purchase totals =	$741.18		$802.5632	$802.56	$802.55	$802.40