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	$250.57	10.614%	$277.1655	$277.17	$277.15	$277.20
Purchase #2	$28.59	12.454%	$32.1506	$32.15	$32.15	$32.20
Purchase #3	$93.71	10.301%	$103.3631	$103.36	$103.35	$103.40
Purchase #4	$33.60	6.212%	$35.6872	$35.69	$35.70	$35.70
Purchase #5	$75.42	4.632%	$78.9135	$78.91	$78.90	$78.90
Purchase #6	$114.28	7.870%	$123.2738	$123.27	$123.25	$123.30
Purchase #7	$207.60	3.660%	$215.1982	$215.20	$215.20	$215.20
7 purchase totals =	$803.77		$865.7519	$865.75	$865.70	$865.90