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	$112.86	5.745%	$119.3438	$119.34	$119.35	$119.30
Purchase #2	$95.48	10.290%	$105.3049	$105.30	$105.30	$105.30
Purchase #3	$62.29	11.294%	$69.325	$69.33	$69.35	$69.30
Purchase #4	$73.47	6.520%	$78.2602	$78.26	$78.25	$78.30
Purchase #5	$117.79	4.621%	$123.2331	$123.23	$123.25	$123.20
Purchase #6	$178.29	10.854%	$197.6416	$197.64	$197.65	$197.60
Purchase #7	$84.42	9.151%	$92.1453	$92.15	$92.15	$92.10
7 purchase totals =	$724.60		$785.2539	$785.25	$785.30	$785.10