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	$182.99	4.377%	$190.9995	$191.00	$191.00	$191.00
Purchase #2	$142.89	4.567%	$149.4158	$149.42	$149.40	$149.40
Purchase #3	$42.51	7.303%	$45.6145	$45.61	$45.60	$45.60
Purchase #4	$78.49	8.385%	$85.0714	$85.07	$85.05	$85.10
Purchase #5	$63.62	11.560%	$70.9745	$70.97	$70.95	$71.00
Purchase #6	$240.31	11.609%	$268.2076	$268.21	$268.20	$268.20
Purchase #7	$150.43	11.734%	$168.0815	$168.08	$168.10	$168.10
7 purchase totals =	$901.24		$978.3648	$978.36	$978.30	$978.40