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	$52.76	4.478%	$55.1226	$55.12	$55.10	$55.10
Purchase #2	$113.70	11.811%	$127.1291	$127.13	$127.15	$127.10
Purchase #3	$220.36	10.834%	$244.2338	$244.23	$244.25	$244.20
Purchase #4	$192.94	3.838%	$200.345	$200.35	$200.35	$200.30
Purchase #5	$111.50	11.366%	$124.1731	$124.17	$124.15	$124.20
Purchase #6	$175.28	3.369%	$181.1852	$181.19	$181.20	$181.20
Purchase #7	$117.96	10.571%	$130.4296	$130.43	$130.45	$130.40
7 purchase totals =	$984.50		$1,062.6184	$1,062.62	$1,062.65	$1,062.50