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	$189.54	4.800%	$198.6379	$198.64	$198.65	$198.60
Purchase #2	$164.35	13.132%	$185.9324	$185.93	$185.95	$185.90
Purchase #3	$150.74	9.286%	$164.7377	$164.74	$164.75	$164.70
Purchase #4	$209.42	4.801%	$219.4743	$219.47	$219.45	$219.50
Purchase #5	$181.48	5.478%	$191.4215	$191.42	$191.40	$191.40
Purchase #6	$37.45	6.395%	$39.8449	$39.84	$39.85	$39.80
Purchase #7	$57.81	9.759%	$63.4517	$63.45	$63.45	$63.50
7 purchase totals =	$990.79		$1,063.5004	$1,063.49	$1,063.50	$1,063.40