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	$41.68	10.871%	$46.211	$46.21	$46.20	$46.20
Purchase #2	$129.72	12.220%	$145.5718	$145.57	$145.55	$145.60
Purchase #3	$93.49	3.210%	$96.491	$96.49	$96.50	$96.50
Purchase #4	$162.89	4.374%	$170.0148	$170.01	$170.00	$170.00
Purchase #5	$229.78	4.874%	$240.9795	$240.98	$241.00	$241.00
Purchase #6	$225.27	5.673%	$238.0496	$238.05	$238.05	$238.00
Purchase #7	$53.72	10.809%	$59.5266	$59.53	$59.55	$59.50
7 purchase totals =	$936.55		$996.8443	$996.84	$996.85	$996.80