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	$83.25	13.770%	$94.7135	$94.71	$94.70	$94.70
Purchase #2	$175.71	9.202%	$191.8788	$191.88	$191.90	$191.90
Purchase #3	$81.33	13.555%	$92.3543	$92.35	$92.35	$92.40
Purchase #4	$142.90	7.227%	$153.2274	$153.23	$153.25	$153.20
Purchase #5	$122.69	4.205%	$127.8491	$127.85	$127.85	$127.80
Purchase #6	$250.82	13.678%	$285.1272	$285.13	$285.15	$285.10
Purchase #7	$205.77	12.409%	$231.304	$231.30	$231.30	$231.30
7 purchase totals =	$1,062.47		$1,176.4543	$1,176.45	$1,176.50	$1,176.40