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	$47.30	13.713%	$53.7862	$53.79	$53.80	$53.80
Purchase #2	$243.82	8.501%	$264.5471	$264.55	$264.55	$264.50
Purchase #3	$186.43	6.472%	$198.4957	$198.50	$198.50	$198.50
Purchase #4	$182.61	4.321%	$190.5006	$190.50	$190.50	$190.50
Purchase #5	$173.71	8.750%	$188.9096	$188.91	$188.90	$188.90
Purchase #6	$54.81	4.754%	$57.4157	$57.42	$57.40	$57.40
Purchase #7	$185.61	7.812%	$200.1099	$200.11	$200.10	$200.10
7 purchase totals =	$1,074.29		$1,153.7648	$1,153.78	$1,153.75	$1,153.70