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	$196.31	11.177%	$218.2516	$218.25	$218.25	$218.30
Purchase #2	$48.71	3.565%	$50.4465	$50.45	$50.45	$50.40
Purchase #3	$244.61	11.740%	$273.3272	$273.33	$273.35	$273.30
Purchase #4	$233.36	8.759%	$253.8	$253.80	$253.80	$253.80
Purchase #5	$174.76	9.213%	$190.8606	$190.86	$190.85	$190.90
Purchase #6	$166.85	9.823%	$183.2397	$183.24	$183.25	$183.20
Purchase #7	$229.61	5.411%	$242.0342	$242.03	$242.05	$242.00
7 purchase totals =	$1,294.21		$1,411.9598	$1,411.96	$1,412.00	$1,411.90