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	$162.83	12.596%	$183.3401	$183.34	$183.35	$183.30
Purchase #2	$64.32	12.166%	$72.1452	$72.15	$72.15	$72.10
Purchase #3	$229.70	11.609%	$256.3659	$256.37	$256.35	$256.40
Purchase #4	$12.62	3.629%	$13.078	$13.08	$13.10	$13.10
Purchase #5	$39.35	7.640%	$42.3563	$42.36	$42.35	$42.40
Purchase #6	$244.38	8.178%	$264.3654	$264.37	$264.35	$264.40
Purchase #7	$187.56	3.414%	$193.9633	$193.96	$193.95	$194.00
7 purchase totals =	$940.76		$1,025.6142	$1,025.63	$1,025.60	$1,025.70