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	$136.40	11.420%	$151.9769	$151.98	$152.00	$152.00
Purchase #2	$79.64	12.425%	$89.5353	$89.54	$89.55	$89.50
Purchase #3	$145.84	6.508%	$155.3313	$155.33	$155.35	$155.30
Purchase #4	$162.60	3.168%	$167.7512	$167.75	$167.75	$167.80
Purchase #5	$219.74	10.423%	$242.6435	$242.64	$242.65	$242.60
Purchase #6	$250.58	6.248%	$266.2362	$266.24	$266.25	$266.20
Purchase #7	$84.45	7.321%	$90.6326	$90.63	$90.65	$90.60
7 purchase totals =	$1,079.25		$1,164.1070	$1,164.11	$1,164.20	$1,164.00