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	$185.60	5.693%	$196.1662	$196.17	$196.15	$196.20
Purchase #2	$62.45	13.822%	$71.0818	$71.08	$71.10	$71.10
Purchase #3	$122.34	11.501%	$136.4103	$136.41	$136.40	$136.40
Purchase #4	$230.89	11.665%	$257.8233	$257.82	$257.80	$257.80
Purchase #5	$120.65	6.562%	$128.5671	$128.57	$128.55	$128.60
Purchase #6	$189.99	13.256%	$215.1751	$215.18	$215.20	$215.20
Purchase #7	$152.67	8.577%	$165.7645	$165.76	$165.75	$165.80
7 purchase totals =	$1,064.59		$1,170.9883	$1,170.99	$1,170.95	$1,171.10