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	$172.51	7.408%	$185.2895	$185.29	$185.30	$185.30
Purchase #2	$47.41	11.465%	$52.8456	$52.85	$52.85	$52.80
Purchase #3	$173.49	7.646%	$186.755	$186.76	$186.75	$186.80
Purchase #4	$128.38	11.571%	$143.2348	$143.23	$143.25	$143.20
Purchase #5	$234.45	6.689%	$250.1324	$250.13	$250.15	$250.10
Purchase #6	$180.49	8.305%	$195.4797	$195.48	$195.50	$195.50
Purchase #7	$134.50	12.253%	$150.9803	$150.98	$151.00	$151.00
7 purchase totals =	$1,071.23		$1,164.7173	$1,164.72	$1,164.80	$1,164.70