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	$229.39	4.769%	$240.3296	$240.33	$240.35	$240.30
Purchase #2	$229.64	4.556%	$240.1024	$240.10	$240.10	$240.10
Purchase #3	$10.71	5.117%	$11.258	$11.26	$11.25	$11.30
Purchase #4	$109.95	8.227%	$118.9956	$119.00	$119.00	$119.00
Purchase #5	$225.86	13.359%	$256.0326	$256.03	$256.05	$256.00
Purchase #6	$64.97	10.650%	$71.8893	$71.89	$71.90	$71.90
Purchase #7	$141.70	8.752%	$154.1016	$154.10	$154.10	$154.10
7 purchase totals =	$1,012.22		$1,092.7091	$1,092.71	$1,092.75	$1,092.70