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	$78.93	4.374%	$82.3824	$82.38	$82.40	$82.40
Purchase #2	$144.31	8.116%	$156.0222	$156.02	$156.00	$156.00
Purchase #3	$157.49	9.550%	$172.5303	$172.53	$172.55	$172.50
Purchase #4	$70.90	13.168%	$80.2361	$80.24	$80.25	$80.20
Purchase #5	$119.84	3.746%	$124.3292	$124.33	$124.35	$124.30
Purchase #6	$65.73	6.720%	$70.1471	$70.15	$70.15	$70.10
Purchase #7	$180.45	6.330%	$191.8725	$191.87	$191.85	$191.90
7 purchase totals =	$817.65		$877.5198	$877.52	$877.55	$877.40