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	$214.89	3.427%	$222.2543	$222.25	$222.25	$222.30
Purchase #2	$241.68	12.655%	$272.2646	$272.26	$272.25	$272.30
Purchase #3	$141.95	10.348%	$156.639	$156.64	$156.65	$156.60
Purchase #4	$32.65	13.844%	$37.1701	$37.17	$37.15	$37.20
Purchase #5	$172.80	13.559%	$196.23	$196.23	$196.25	$196.20
Purchase #6	$133.50	9.690%	$146.4362	$146.44	$146.45	$146.40
Purchase #7	$136.98	9.830%	$150.4451	$150.45	$150.45	$150.40
7 purchase totals =	$1,074.45		$1,181.4393	$1,181.44	$1,181.45	$1,181.40