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	$171.51	12.812%	$193.4839	$193.48	$193.50	$193.50
Purchase #2	$154.38	8.266%	$167.1411	$167.14	$167.15	$167.10
Purchase #3	$182.69	8.827%	$198.816	$198.82	$198.80	$198.80
Purchase #4	$194.62	10.637%	$215.3217	$215.32	$215.30	$215.30
Purchase #5	$170.89	7.148%	$183.1052	$183.11	$183.10	$183.10
Purchase #6	$183.37	3.144%	$189.1352	$189.14	$189.15	$189.10
Purchase #7	$50.56	5.714%	$53.449	$53.45	$53.45	$53.40
7 purchase totals =	$1,108.02		$1,200.4521	$1,200.46	$1,200.45	$1,200.30