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	$168.45	6.811%	$179.9231	$179.92	$179.90	$179.90
Purchase #2	$158.69	7.821%	$171.1011	$171.10	$171.10	$171.10
Purchase #3	$95.38	9.369%	$104.3162	$104.32	$104.30	$104.30
Purchase #4	$60.63	5.497%	$63.9628	$63.96	$63.95	$64.00
Purchase #5	$55.82	6.144%	$59.2496	$59.25	$59.25	$59.20
Purchase #6	$59.53	11.540%	$66.3998	$66.40	$66.40	$66.40
Purchase #7	$117.69	11.445%	$131.1596	$131.16	$131.15	$131.20
7 purchase totals =	$716.19		$776.1122	$776.11	$776.05	$776.10