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	$188.63	8.296%	$204.2787	$204.28	$204.30	$204.30
Purchase #2	$18.64	10.335%	$20.5664	$20.57	$20.55	$20.60
Purchase #3	$45.63	8.501%	$49.509	$49.51	$49.50	$49.50
Purchase #4	$224.93	10.760%	$249.1325	$249.13	$249.15	$249.10
Purchase #5	$156.38	7.803%	$168.5823	$168.58	$168.60	$168.60
Purchase #6	$155.55	11.850%	$173.9827	$173.98	$174.00	$174.00
Purchase #7	$163.55	13.423%	$185.5033	$185.50	$185.50	$185.50
7 purchase totals =	$953.31		$1,051.5549	$1,051.55	$1,051.60	$1,051.60