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	$167.78	11.631%	$187.2945	$187.29	$187.30	$187.30
Purchase #2	$99.46	4.478%	$103.9138	$103.91	$103.90	$103.90
Purchase #3	$227.72	9.120%	$248.4881	$248.49	$248.50	$248.50
Purchase #4	$216.78	8.282%	$234.7337	$234.73	$234.75	$234.70
Purchase #5	$94.46	6.554%	$100.6509	$100.65	$100.65	$100.70
Purchase #6	$201.37	5.170%	$211.7808	$211.78	$211.80	$211.80
Purchase #7	$85.63	10.369%	$94.509	$94.51	$94.50	$94.50
7 purchase totals =	$1,093.20		$1,181.3708	$1,181.36	$1,181.40	$1,181.40