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	$142.83	8.607%	$155.1234	$155.12	$155.10	$155.10
Purchase #2	$211.79	12.122%	$237.4632	$237.46	$237.45	$237.50
Purchase #3	$226.97	8.175%	$245.5248	$245.52	$245.50	$245.50
Purchase #4	$161.81	6.790%	$172.7969	$172.80	$172.80	$172.80
Purchase #5	$24.29	8.810%	$26.4299	$26.43	$26.45	$26.40
Purchase #6	$174.96	12.475%	$196.7863	$196.79	$196.80	$196.80
Purchase #7	$137.64	10.773%	$152.468	$152.47	$152.45	$152.50
7 purchase totals =	$1,080.29		$1,186.5925	$1,186.59	$1,186.55	$1,186.60