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	$67.42	9.371%	$73.7379	$73.74	$73.75	$73.70
Purchase #2	$242.93	12.517%	$273.3375	$273.34	$273.35	$273.30
Purchase #3	$87.79	3.519%	$90.8793	$90.88	$90.90	$90.90
Purchase #4	$21.49	6.199%	$22.8222	$22.82	$22.80	$22.80
Purchase #5	$43.76	6.167%	$46.4587	$46.46	$46.45	$46.50
Purchase #6	$95.49	11.330%	$106.309	$106.31	$106.30	$106.30
Purchase #7	$86.98	6.784%	$92.8807	$92.88	$92.90	$92.90
7 purchase totals =	$645.86		$706.4253	$706.43	$706.45	$706.40