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	$186.65	11.560%	$208.2267	$208.23	$208.25	$208.20
Purchase #2	$38.42	9.697%	$42.1456	$42.15	$42.15	$42.10
Purchase #3	$157.55	3.694%	$163.3699	$163.37	$163.35	$163.40
Purchase #4	$98.73	11.171%	$109.7591	$109.76	$109.75	$109.80
Purchase #5	$232.77	13.612%	$264.4547	$264.45	$264.45	$264.50
Purchase #6	$163.92	11.500%	$182.7708	$182.77	$182.75	$182.80
Purchase #7	$31.29	6.437%	$33.3041	$33.30	$33.30	$33.30
7 purchase totals =	$909.33		$1,004.0309	$1,004.03	$1,004.00	$1,004.10