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	$77.72	4.367%	$81.114	$81.11	$81.10	$81.10
Purchase #2	$71.62	8.335%	$77.5895	$77.59	$77.60	$77.60
Purchase #3	$84.71	13.678%	$96.2966	$96.30	$96.30	$96.30
Purchase #4	$25.85	9.454%	$28.2939	$28.29	$28.30	$28.30
Purchase #5	$62.38	3.844%	$64.7779	$64.78	$64.80	$64.80
Purchase #6	$192.51	6.728%	$205.4621	$205.46	$205.45	$205.50
Purchase #7	$29.81	12.688%	$33.5923	$33.59	$33.60	$33.60
7 purchase totals =	$544.60		$587.1263	$587.12	$587.15	$587.20