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	$126.45	3.259%	$130.571	$130.57	$130.55	$130.60
Purchase #2	$66.33	7.404%	$71.2411	$71.24	$71.25	$71.20
Purchase #3	$78.91	3.863%	$81.9583	$81.96	$81.95	$82.00
Purchase #4	$36.96	3.637%	$38.3042	$38.30	$38.30	$38.30
Purchase #5	$137.44	3.765%	$142.6146	$142.61	$142.60	$142.60
Purchase #6	$222.79	4.650%	$233.1497	$233.15	$233.15	$233.10
Purchase #7	$12.70	12.372%	$14.2712	$14.27	$14.25	$14.30
7 purchase totals =	$681.58		$712.1101	$712.10	$712.05	$712.10