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	$158.77	4.559%	$166.0083	$166.01	$166.00	$166.00
Purchase #2	$47.84	11.618%	$53.3981	$53.40	$53.40	$53.40
Purchase #3	$133.44	8.860%	$145.2628	$145.26	$145.25	$145.30
Purchase #4	$102.86	8.786%	$111.8973	$111.90	$111.90	$111.90
Purchase #5	$118.35	8.543%	$128.4606	$128.46	$128.45	$128.50
Purchase #6	$193.87	13.135%	$219.3348	$219.33	$219.35	$219.30
Purchase #7	$57.56	7.348%	$61.7895	$61.79	$61.80	$61.80
7 purchase totals =	$812.69		$886.1514	$886.15	$886.15	$886.20