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	$189.38	12.114%	$212.3215	$212.32	$212.30	$212.30
Purchase #2	$233.79	4.631%	$244.6168	$244.62	$244.60	$244.60
Purchase #3	$29.27	10.221%	$32.2617	$32.26	$32.25	$32.30
Purchase #4	$160.81	4.289%	$167.7071	$167.71	$167.70	$167.70
Purchase #5	$125.36	4.861%	$131.4537	$131.45	$131.45	$131.50
Purchase #6	$25.77	5.192%	$27.108	$27.11	$27.10	$27.10
Purchase #7	$174.99	6.160%	$185.7694	$185.77	$185.75	$185.80
7 purchase totals =	$939.37		$1,001.2382	$1,001.24	$1,001.15	$1,001.30