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	$87.47	4.605%	$91.498	$91.50	$91.50	$91.50
Purchase #2	$202.91	4.711%	$212.4691	$212.47	$212.45	$212.50
Purchase #3	$11.87	13.839%	$13.5127	$13.51	$13.50	$13.50
Purchase #4	$73.33	7.418%	$78.7696	$78.77	$78.75	$78.80
Purchase #5	$211.87	6.368%	$225.3619	$225.36	$225.35	$225.40
Purchase #6	$76.44	9.574%	$83.7584	$83.76	$83.75	$83.80
Purchase #7	$60.31	7.780%	$65.0021	$65.00	$65.00	$65.00
7 purchase totals =	$724.20		$770.3718	$770.37	$770.30	$770.50