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	$126.88	12.522%	$142.7679	$142.77	$142.75	$142.80
Purchase #2	$76.31	11.392%	$85.0032	$85.00	$85.00	$85.00
Purchase #3	$121.41	12.127%	$136.1334	$136.13	$136.15	$136.10
Purchase #4	$161.61	8.236%	$174.9202	$174.92	$174.90	$174.90
Purchase #5	$55.49	11.537%	$61.8919	$61.89	$61.90	$61.90
Purchase #6	$229.30	7.648%	$246.8369	$246.84	$246.85	$246.80
Purchase #7	$204.91	11.824%	$229.1386	$229.14	$229.15	$229.10
7 purchase totals =	$975.91		$1,076.6921	$1,076.69	$1,076.70	$1,076.60