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	$112.98	11.830%	$126.3455	$126.35	$126.35	$126.30
Purchase #2	$55.96	11.540%	$62.4178	$62.42	$62.40	$62.40
Purchase #3	$218.68	9.363%	$239.155	$239.16	$239.15	$239.20
Purchase #4	$90.53	13.148%	$102.4329	$102.43	$102.45	$102.40
Purchase #5	$117.31	8.490%	$127.2696	$127.27	$127.25	$127.30
Purchase #6	$61.72	5.786%	$65.2911	$65.29	$65.30	$65.30
Purchase #7	$229.68	10.655%	$254.1524	$254.15	$254.15	$254.20
7 purchase totals =	$886.86		$977.0643	$977.07	$977.05	$977.10