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	$158.47	8.843%	$172.4835	$172.48	$172.50	$172.50
Purchase #2	$136.39	3.466%	$141.1173	$141.12	$141.10	$141.10
Purchase #3	$99.80	3.539%	$103.3319	$103.33	$103.35	$103.30
Purchase #4	$203.39	11.772%	$227.3331	$227.33	$227.35	$227.30
Purchase #5	$60.84	8.351%	$65.9207	$65.92	$65.90	$65.90
Purchase #6	$118.58	8.224%	$128.332	$128.33	$128.35	$128.30
Purchase #7	$58.50	13.331%	$66.2986	$66.30	$66.30	$66.30
7 purchase totals =	$835.97		$904.8171	$904.81	$904.85	$904.70