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	$199.30	6.794%	$212.8404	$212.84	$212.85	$212.80
Purchase #2	$130.55	5.448%	$137.6624	$137.66	$137.65	$137.70
Purchase #3	$186.86	9.213%	$204.0754	$204.08	$204.10	$204.10
Purchase #4	$6.77	4.267%	$7.0589	$7.06	$7.05	$7.10
Purchase #5	$72.59	8.234%	$78.5671	$78.57	$78.55	$78.60
Purchase #6	$210.58	5.172%	$221.4712	$221.47	$221.45	$221.50
Purchase #7	$131.86	5.687%	$139.3589	$139.36	$139.35	$139.40
7 purchase totals =	$938.51		$1,001.0343	$1,001.04	$1,001.00	$1,001.20