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	$73.30	4.634%	$76.6967	$76.70	$76.70	$76.70
Purchase #2	$235.92	13.855%	$268.6067	$268.61	$268.60	$268.60
Purchase #3	$86.42	12.790%	$97.4731	$97.47	$97.45	$97.50
Purchase #4	$211.76	3.468%	$219.1038	$219.10	$219.10	$219.10
Purchase #5	$189.81	5.649%	$200.5324	$200.53	$200.55	$200.50
Purchase #6	$97.73	4.116%	$101.7526	$101.75	$101.75	$101.80
Purchase #7	$172.51	13.694%	$196.1335	$196.13	$196.15	$196.10
7 purchase totals =	$1,067.45		$1,160.2988	$1,160.29	$1,160.30	$1,160.30