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	$85.46	10.628%	$94.5427	$94.54	$94.55	$94.50
Purchase #2	$220.25	4.154%	$229.3992	$229.40	$229.40	$229.40
Purchase #3	$28.78	12.516%	$32.3821	$32.38	$32.40	$32.40
Purchase #4	$241.37	12.333%	$271.1382	$271.14	$271.15	$271.10
Purchase #5	$29.60	13.260%	$33.525	$33.53	$33.55	$33.50
Purchase #6	$190.57	11.201%	$211.9157	$211.92	$211.90	$211.90
Purchase #7	$154.92	6.431%	$164.8829	$164.88	$164.90	$164.90
7 purchase totals =	$950.95		$1,037.7858	$1,037.79	$1,037.85	$1,037.70