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	$189.72	10.209%	$209.0885	$209.09	$209.10	$209.10
Purchase #2	$81.48	5.242%	$85.7512	$85.75	$85.75	$85.80
Purchase #3	$129.64	10.737%	$143.5594	$143.56	$143.55	$143.60
Purchase #4	$53.54	4.640%	$56.0243	$56.02	$56.00	$56.00
Purchase #5	$47.85	11.439%	$53.3236	$53.32	$53.30	$53.30
Purchase #6	$80.42	6.642%	$85.7615	$85.76	$85.75	$85.80
Purchase #7	$80.27	13.518%	$91.1209	$91.12	$91.10	$91.10
7 purchase totals =	$662.92		$724.6294	$724.62	$724.55	$724.70