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	$47.77	11.608%	$53.3151	$53.32	$53.30	$53.30
Purchase #2	$102.55	7.519%	$110.2607	$110.26	$110.25	$110.30
Purchase #3	$80.75	3.120%	$83.2694	$83.27	$83.25	$83.30
Purchase #4	$211.52	13.274%	$239.5972	$239.60	$239.60	$239.60
Purchase #5	$230.64	5.632%	$243.6296	$243.63	$243.65	$243.60
Purchase #6	$125.72	8.414%	$136.2981	$136.30	$136.30	$136.30
Purchase #7	$209.65	4.866%	$219.8516	$219.85	$219.85	$219.90
7 purchase totals =	$1,008.60		$1,086.2217	$1,086.23	$1,086.20	$1,086.30