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	$169.45	10.602%	$187.4151	$187.42	$187.40	$187.40
Purchase #2	$209.48	11.669%	$233.9242	$233.92	$233.90	$233.90
Purchase #3	$89.92	11.376%	$100.1493	$100.15	$100.15	$100.10
Purchase #4	$134.57	9.156%	$146.8912	$146.89	$146.90	$146.90
Purchase #5	$169.46	3.633%	$175.6165	$175.62	$175.60	$175.60
Purchase #6	$51.69	9.155%	$56.4222	$56.42	$56.40	$56.40
Purchase #7	$106.33	6.142%	$112.8608	$112.86	$112.85	$112.90
7 purchase totals =	$930.90		$1,013.2793	$1,013.28	$1,013.20	$1,013.20