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	$61.79	8.618%	$67.1151	$67.12	$67.10	$67.10
Purchase #2	$41.50	8.157%	$44.8852	$44.89	$44.90	$44.90
Purchase #3	$98.92	12.831%	$111.6124	$111.61	$111.60	$111.60
Purchase #4	$165.82	3.400%	$171.4579	$171.46	$171.45	$171.50
Purchase #5	$41.77	10.781%	$46.2732	$46.27	$46.25	$46.30
Purchase #6	$139.91	8.412%	$151.6792	$151.68	$151.70	$151.70
Purchase #7	$178.62	8.681%	$194.126	$194.13	$194.15	$194.10
7 purchase totals =	$728.33		$787.1490	$787.16	$787.15	$787.20