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	$103.99	5.742%	$109.9611	$109.96	$109.95	$110.00
Purchase #2	$53.47	12.274%	$60.0329	$60.03	$60.05	$60.00
Purchase #3	$154.76	8.841%	$168.4423	$168.44	$168.45	$168.40
Purchase #4	$165.41	8.318%	$179.1688	$179.17	$179.15	$179.20
Purchase #5	$89.33	11.369%	$99.4859	$99.49	$99.50	$99.50
Purchase #6	$8.52	10.480%	$9.4129	$9.41	$9.40	$9.40
Purchase #7	$75.26	4.164%	$78.3938	$78.39	$78.40	$78.40
7 purchase totals =	$650.74		$704.8977	$704.89	$704.90	$704.90