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	$189.69	4.784%	$198.7648	$198.76	$198.75	$198.80
Purchase #2	$87.49	13.529%	$99.3265	$99.33	$99.35	$99.30
Purchase #3	$59.51	10.568%	$65.799	$65.80	$65.80	$65.80
Purchase #4	$42.93	5.581%	$45.3259	$45.33	$45.35	$45.30
Purchase #5	$37.97	10.726%	$42.0427	$42.04	$42.05	$42.00
Purchase #6	$80.51	8.656%	$87.4789	$87.48	$87.50	$87.50
Purchase #7	$188.41	12.223%	$211.4394	$211.44	$211.45	$211.40
7 purchase totals =	$686.51		$750.1772	$750.18	$750.25	$750.10