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	$181.56	12.228%	$203.7612	$203.76	$203.75	$203.80
Purchase #2	$114.60	11.146%	$127.3733	$127.37	$127.35	$127.40
Purchase #3	$26.35	5.722%	$27.8577	$27.86	$27.85	$27.90
Purchase #4	$64.83	8.170%	$70.1266	$70.13	$70.15	$70.10
Purchase #5	$103.76	10.171%	$114.3134	$114.31	$114.30	$114.30
Purchase #6	$92.87	8.221%	$100.5048	$100.50	$100.50	$100.50
Purchase #7	$112.89	4.765%	$118.2692	$118.27	$118.25	$118.30
7 purchase totals =	$696.86		$762.2062	$762.20	$762.15	$762.30