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	$172.85	10.773%	$191.4711	$191.47	$191.45	$191.50
Purchase #2	$209.88	10.736%	$232.4127	$232.41	$232.40	$232.40
Purchase #3	$23.98	7.529%	$25.7855	$25.79	$25.80	$25.80
Purchase #4	$51.93	4.343%	$54.1853	$54.19	$54.20	$54.20
Purchase #5	$50.47	7.577%	$54.2941	$54.29	$54.30	$54.30
Purchase #6	$208.74	4.631%	$218.4067	$218.41	$218.40	$218.40
Purchase #7	$223.86	6.694%	$238.8452	$238.85	$238.85	$238.80
7 purchase totals =	$941.71		$1,015.4006	$1,015.41	$1,015.40	$1,015.40