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	$86.57	4.766%	$90.6959	$90.70	$90.70	$90.70
Purchase #2	$156.37	5.453%	$164.8969	$164.90	$164.90	$164.90
Purchase #3	$142.73	5.304%	$150.3004	$150.30	$150.30	$150.30
Purchase #4	$101.84	6.295%	$108.2508	$108.25	$108.25	$108.30
Purchase #5	$68.71	13.187%	$77.7708	$77.77	$77.75	$77.80
Purchase #6	$19.75	5.235%	$20.7839	$20.78	$20.80	$20.80
Purchase #7	$110.33	9.364%	$120.6613	$120.66	$120.65	$120.70
7 purchase totals =	$686.30		$733.3600	$733.36	$733.35	$733.50