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	$55.60	12.498%	$62.5489	$62.55	$62.55	$62.50
Purchase #2	$90.33	12.296%	$101.437	$101.44	$101.45	$101.40
Purchase #3	$56.59	8.374%	$61.3288	$61.33	$61.35	$61.30
Purchase #4	$195.53	12.161%	$219.3084	$219.31	$219.30	$219.30
Purchase #5	$249.46	3.185%	$257.4053	$257.41	$257.40	$257.40
Purchase #6	$151.95	12.809%	$171.4133	$171.41	$171.40	$171.40
Purchase #7	$187.28	13.847%	$213.2127	$213.21	$213.20	$213.20
7 purchase totals =	$986.74		$1,086.6544	$1,086.66	$1,086.65	$1,086.50