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	$156.63	7.409%	$168.2347	$168.23	$168.25	$168.20
Purchase #2	$6.43	11.251%	$7.1534	$7.15	$7.15	$7.20
Purchase #3	$38.45	9.129%	$41.9601	$41.96	$41.95	$42.00
Purchase #4	$108.85	6.132%	$115.5247	$115.52	$115.50	$115.50
Purchase #5	$132.72	5.843%	$140.4748	$140.47	$140.45	$140.50
Purchase #6	$121.65	6.168%	$129.1534	$129.15	$129.15	$129.20
Purchase #7	$174.96	6.297%	$185.9772	$185.98	$186.00	$186.00
7 purchase totals =	$739.69		$788.4783	$788.46	$788.45	$788.60