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	$53.76	3.499%	$55.6411	$55.64	$55.65	$55.60
Purchase #2	$73.51	3.542%	$76.1137	$76.11	$76.10	$76.10
Purchase #3	$199.34	5.510%	$210.3236	$210.32	$210.30	$210.30
Purchase #4	$165.66	8.405%	$179.5837	$179.58	$179.60	$179.60
Purchase #5	$234.66	7.849%	$253.0785	$253.08	$253.10	$253.10
Purchase #6	$180.90	13.607%	$205.5151	$205.52	$205.50	$205.50
Purchase #7	$65.63	10.219%	$72.3367	$72.34	$72.35	$72.30
7 purchase totals =	$973.46		$1,052.5924	$1,052.59	$1,052.60	$1,052.50