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	$44.99	5.305%	$47.3767	$47.38	$47.40	$47.40
Purchase #2	$202.49	4.603%	$211.8106	$211.81	$211.80	$211.80
Purchase #3	$55.37	4.797%	$58.0261	$58.03	$58.05	$58.00
Purchase #4	$53.91	9.827%	$59.2077	$59.21	$59.20	$59.20
Purchase #5	$100.90	3.488%	$104.4194	$104.42	$104.40	$104.40
Purchase #6	$233.82	9.739%	$256.5917	$256.59	$256.60	$256.60
Purchase #7	$247.92	13.678%	$281.8305	$281.83	$281.85	$281.80
7 purchase totals =	$939.40		$1,019.2627	$1,019.27	$1,019.30	$1,019.20