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	$50.54	6.482%	$53.816	$53.82	$53.80	$53.80
Purchase #2	$84.72	6.705%	$90.4005	$90.40	$90.40	$90.40
Purchase #3	$70.91	3.239%	$73.2068	$73.21	$73.20	$73.20
Purchase #4	$245.76	4.361%	$256.4776	$256.48	$256.50	$256.50
Purchase #5	$121.54	10.710%	$134.5569	$134.56	$134.55	$134.60
Purchase #6	$93.93	4.745%	$98.387	$98.39	$98.40	$98.40
Purchase #7	$234.39	6.764%	$250.2441	$250.24	$250.25	$250.20
7 purchase totals =	$901.79		$957.0889	$957.10	$957.10	$957.10