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	$178.48	10.220%	$196.7207	$196.72	$196.70	$196.70
Purchase #2	$117.26	8.389%	$127.0969	$127.10	$127.10	$127.10
Purchase #3	$132.84	6.568%	$141.5649	$141.56	$141.55	$141.60
Purchase #4	$154.33	9.720%	$169.3309	$169.33	$169.35	$169.30
Purchase #5	$71.57	12.124%	$80.2471	$80.25	$80.25	$80.20
Purchase #6	$53.59	12.769%	$60.4329	$60.43	$60.45	$60.40
Purchase #7	$219.73	10.301%	$242.3644	$242.36	$242.35	$242.40
7 purchase totals =	$927.80		$1,017.7578	$1,017.75	$1,017.75	$1,017.70