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	$53.48	10.751%	$59.2296	$59.23	$59.25	$59.20
Purchase #2	$189.78	7.726%	$204.4424	$204.44	$204.45	$204.40
Purchase #3	$74.47	10.416%	$82.2268	$82.23	$82.25	$82.20
Purchase #4	$27.60	10.633%	$30.5347	$30.53	$30.55	$30.50
Purchase #5	$56.93	13.663%	$64.7083	$64.71	$64.70	$64.70
Purchase #6	$63.83	13.760%	$72.613	$72.61	$72.60	$72.60
Purchase #7	$173.54	6.311%	$184.4921	$184.49	$184.50	$184.50
7 purchase totals =	$639.63		$698.2469	$698.24	$698.30	$698.10