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	$187.67	3.559%	$194.3492	$194.35	$194.35	$194.30
Purchase #2	$52.86	11.797%	$59.0959	$59.10	$59.10	$59.10
Purchase #3	$207.25	12.665%	$233.4982	$233.50	$233.50	$233.50
Purchase #4	$65.91	3.363%	$68.1266	$68.13	$68.15	$68.10
Purchase #5	$244.91	8.670%	$266.1437	$266.14	$266.15	$266.10
Purchase #6	$245.90	11.216%	$273.4801	$273.48	$273.50	$273.50
Purchase #7	$136.95	7.353%	$147.0199	$147.02	$147.00	$147.00
7 purchase totals =	$1,141.45		$1,241.7136	$1,241.72	$1,241.75	$1,241.60