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	$248.84	5.173%	$261.7125	$261.71	$261.70	$261.70
Purchase #2	$26.43	8.124%	$28.5772	$28.58	$28.60	$28.60
Purchase #3	$156.29	7.167%	$167.4913	$167.49	$167.50	$167.50
Purchase #4	$89.92	3.185%	$92.784	$92.78	$92.80	$92.80
Purchase #5	$142.83	6.148%	$151.6112	$151.61	$151.60	$151.60
Purchase #6	$10.91	3.621%	$11.3051	$11.31	$11.30	$11.30
Purchase #7	$210.56	8.627%	$228.725	$228.73	$228.75	$228.70
7 purchase totals =	$885.78		$942.2063	$942.21	$942.25	$942.20