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	$84.89	13.488%	$96.34	$96.34	$96.35	$96.30
Purchase #2	$27.74	3.204%	$28.6288	$28.63	$28.65	$28.60
Purchase #3	$77.36	13.611%	$87.8895	$87.89	$87.90	$87.90
Purchase #4	$187.98	12.137%	$210.7951	$210.80	$210.80	$210.80
Purchase #5	$59.29	5.847%	$62.7567	$62.76	$62.75	$62.80
Purchase #6	$28.41	11.218%	$31.597	$31.60	$31.60	$31.60
Purchase #7	$197.82	12.653%	$222.8502	$222.85	$222.85	$222.90
7 purchase totals =	$663.49		$740.8573	$740.87	$740.90	$740.90