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	$166.68	11.173%	$185.3032	$185.30	$185.30	$185.30
Purchase #2	$14.42	3.187%	$14.8796	$14.88	$14.90	$14.90
Purchase #3	$24.36	12.357%	$27.3702	$27.37	$27.35	$27.40
Purchase #4	$214.46	9.486%	$234.8037	$234.80	$234.80	$234.80
Purchase #5	$98.73	12.494%	$111.0653	$111.07	$111.05	$111.10
Purchase #6	$48.61	6.795%	$51.913	$51.91	$51.90	$51.90
Purchase #7	$130.25	5.413%	$137.3004	$137.30	$137.30	$137.30
7 purchase totals =	$697.51		$762.6354	$762.63	$762.60	$762.70