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	$210.55	4.549%	$220.1279	$220.13	$220.15	$220.10
Purchase #2	$81.82	11.578%	$91.2931	$91.29	$91.30	$91.30
Purchase #3	$202.42	7.745%	$218.0974	$218.10	$218.10	$218.10
Purchase #4	$50.26	11.681%	$56.1309	$56.13	$56.15	$56.10
Purchase #5	$180.59	4.147%	$188.0791	$188.08	$188.10	$188.10
Purchase #6	$70.33	12.158%	$78.8807	$78.88	$78.90	$78.90
Purchase #7	$88.65	12.720%	$99.9263	$99.93	$99.95	$99.90
7 purchase totals =	$884.62		$952.5354	$952.54	$952.65	$952.50