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	$100.54	9.516%	$110.1074	$110.11	$110.10	$110.10
Purchase #2	$208.71	4.611%	$218.3336	$218.33	$218.35	$218.30
Purchase #3	$90.76	11.152%	$100.8816	$100.88	$100.90	$100.90
Purchase #4	$30.66	6.809%	$32.7476	$32.75	$32.75	$32.70
Purchase #5	$210.82	7.132%	$225.8557	$225.86	$225.85	$225.90
Purchase #6	$211.25	13.758%	$240.3138	$240.31	$240.30	$240.30
Purchase #7	$245.41	11.328%	$273.21	$273.21	$273.20	$273.20
7 purchase totals =	$1,098.15		$1,201.4497	$1,201.45	$1,201.45	$1,201.40