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	$168.55	10.271%	$185.8618	$185.86	$185.85	$185.90
Purchase #2	$221.56	7.578%	$238.3498	$238.35	$238.35	$238.30
Purchase #3	$190.90	4.777%	$200.0193	$200.02	$200.00	$200.00
Purchase #4	$97.41	7.112%	$104.3378	$104.34	$104.35	$104.30
Purchase #5	$184.40	13.750%	$209.755	$209.76	$209.75	$209.80
Purchase #6	$135.99	5.168%	$143.018	$143.02	$143.00	$143.00
Purchase #7	$6.31	12.741%	$7.114	$7.11	$7.10	$7.10
7 purchase totals =	$1,005.12		$1,088.4557	$1,088.46	$1,088.40	$1,088.40