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	$209.31	3.780%	$217.2219	$217.22	$217.20	$217.20
Purchase #2	$196.83	7.754%	$212.0922	$212.09	$212.10	$212.10
Purchase #3	$137.84	12.802%	$155.4863	$155.49	$155.50	$155.50
Purchase #4	$185.72	5.839%	$196.5642	$196.56	$196.55	$196.60
Purchase #5	$98.25	4.274%	$102.4492	$102.45	$102.45	$102.40
Purchase #6	$211.74	7.558%	$227.7433	$227.74	$227.75	$227.70
Purchase #7	$70.89	5.472%	$74.7691	$74.77	$74.75	$74.80
7 purchase totals =	$1,110.58		$1,186.3262	$1,186.32	$1,186.30	$1,186.30