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	$133.91	13.680%	$152.2289	$152.23	$152.25	$152.20
Purchase #2	$22.42	3.278%	$23.1549	$23.15	$23.15	$23.20
Purchase #3	$93.28	6.493%	$99.3367	$99.34	$99.35	$99.30
Purchase #4	$167.59	12.381%	$188.3393	$188.34	$188.35	$188.30
Purchase #5	$162.53	4.529%	$169.891	$169.89	$169.90	$169.90
Purchase #6	$70.26	3.396%	$72.646	$72.65	$72.65	$72.60
Purchase #7	$64.80	10.414%	$71.5483	$71.55	$71.55	$71.50
7 purchase totals =	$714.79		$777.1451	$777.15	$777.20	$777.00