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	$82.65	8.567%	$89.7306	$89.73	$89.75	$89.70
Purchase #2	$229.38	3.707%	$237.8831	$237.88	$237.90	$237.90
Purchase #3	$117.46	9.276%	$128.3556	$128.36	$128.35	$128.40
Purchase #4	$230.69	13.502%	$261.8378	$261.84	$261.85	$261.80
Purchase #5	$78.78	12.443%	$88.5826	$88.58	$88.60	$88.60
Purchase #6	$154.88	3.376%	$160.1087	$160.11	$160.10	$160.10
Purchase #7	$73.63	13.585%	$83.6326	$83.63	$83.65	$83.60
7 purchase totals =	$967.47		$1,050.1310	$1,050.13	$1,050.20	$1,050.10