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	$7.64	3.181%	$7.883	$7.88	$7.90	$7.90
Purchase #2	$22.57	11.382%	$25.1389	$25.14	$25.15	$25.10
Purchase #3	$7.70	5.800%	$8.1466	$8.15	$8.15	$8.10
Purchase #4	$69.58	5.402%	$73.3387	$73.34	$73.35	$73.30
Purchase #5	$85.71	4.590%	$89.6441	$89.64	$89.65	$89.60
Purchase #6	$70.33	11.764%	$78.6036	$78.60	$78.60	$78.60
Purchase #7	$53.41	4.357%	$55.7371	$55.74	$55.75	$55.70
7 purchase totals =	$316.94		$338.4920	$338.49	$338.55	$338.30