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	$246.39	5.438%	$259.7887	$259.79	$259.80	$259.80
Purchase #2	$219.92	6.119%	$233.3769	$233.38	$233.40	$233.40
Purchase #3	$121.85	10.174%	$134.247	$134.25	$134.25	$134.20
Purchase #4	$89.54	10.831%	$99.2381	$99.24	$99.25	$99.20
Purchase #5	$47.90	10.547%	$52.952	$52.95	$52.95	$53.00
Purchase #6	$39.65	4.825%	$41.5631	$41.56	$41.55	$41.60
Purchase #7	$186.73	4.114%	$194.4121	$194.41	$194.40	$194.40
7 purchase totals =	$951.98		$1,015.5779	$1,015.58	$1,015.60	$1,015.60