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	$96.77	8.414%	$104.9122	$104.91	$104.90	$104.90
Purchase #2	$236.64	10.784%	$262.1593	$262.16	$262.15	$262.20
Purchase #3	$57.90	3.368%	$59.8501	$59.85	$59.85	$59.90
Purchase #4	$28.47	12.812%	$32.1176	$32.12	$32.10	$32.10
Purchase #5	$210.61	8.525%	$228.5645	$228.56	$228.55	$228.60
Purchase #6	$190.93	13.264%	$216.255	$216.26	$216.25	$216.30
Purchase #7	$191.45	4.164%	$199.422	$199.42	$199.40	$199.40
7 purchase totals =	$1,012.77		$1,103.2807	$1,103.28	$1,103.20	$1,103.40