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	$6.98	5.288%	$7.3491	$7.35	$7.35	$7.30
Purchase #2	$135.84	11.532%	$151.5051	$151.51	$151.50	$151.50
Purchase #3	$55.55	7.620%	$59.7829	$59.78	$59.80	$59.80
Purchase #4	$101.69	3.274%	$105.0193	$105.02	$105.00	$105.00
Purchase #5	$179.48	4.734%	$187.9766	$187.98	$188.00	$188.00
Purchase #6	$227.65	9.415%	$249.0832	$249.08	$249.10	$249.10
Purchase #7	$222.44	5.110%	$233.8067	$233.81	$233.80	$233.80
7 purchase totals =	$929.63		$994.5229	$994.53	$994.55	$994.50