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	$98.25	11.871%	$109.9133	$109.91	$109.90	$109.90
Purchase #2	$131.87	3.780%	$136.8547	$136.85	$136.85	$136.90
Purchase #3	$173.51	13.824%	$197.496	$197.50	$197.50	$197.50
Purchase #4	$86.95	4.800%	$91.1236	$91.12	$91.10	$91.10
Purchase #5	$193.64	12.753%	$218.3349	$218.33	$218.35	$218.30
Purchase #6	$64.47	7.536%	$69.3285	$69.33	$69.35	$69.30
Purchase #7	$242.48	12.740%	$273.372	$273.37	$273.35	$273.40
7 purchase totals =	$991.17		$1,096.4230	$1,096.41	$1,096.40	$1,096.40