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	$165.55	9.236%	$180.8402	$180.84	$180.85	$180.80
Purchase #2	$178.43	6.766%	$190.5026	$190.50	$190.50	$190.50
Purchase #3	$136.58	13.205%	$154.6154	$154.62	$154.60	$154.60
Purchase #4	$142.67	5.251%	$150.1616	$150.16	$150.15	$150.20
Purchase #5	$148.40	13.662%	$168.6744	$168.67	$168.65	$168.70
Purchase #6	$106.48	3.141%	$109.8245	$109.82	$109.80	$109.80
Purchase #7	$89.91	3.818%	$93.3428	$93.34	$93.35	$93.30
7 purchase totals =	$968.02		$1,047.9615	$1,047.95	$1,047.90	$1,047.90