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	$55.98	12.173%	$62.7944	$62.79	$62.80	$62.80
Purchase #2	$194.54	3.549%	$201.4442	$201.44	$201.45	$201.40
Purchase #3	$186.66	11.130%	$207.4353	$207.44	$207.45	$207.40
Purchase #4	$248.55	10.705%	$275.1573	$275.16	$275.15	$275.20
Purchase #5	$59.85	5.848%	$63.35	$63.35	$63.35	$63.40
Purchase #6	$28.47	10.484%	$31.4548	$31.45	$31.45	$31.50
Purchase #7	$72.77	13.717%	$82.7519	$82.75	$82.75	$82.80
7 purchase totals =	$846.82		$924.3879	$924.38	$924.40	$924.50