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	$198.97	8.256%	$215.397	$215.40	$215.40	$215.40
Purchase #2	$33.74	10.493%	$37.2803	$37.28	$37.30	$37.30
Purchase #3	$189.40	11.607%	$211.3837	$211.38	$211.40	$211.40
Purchase #4	$64.38	11.466%	$71.7618	$71.76	$71.75	$71.80
Purchase #5	$235.56	5.525%	$248.5747	$248.57	$248.55	$248.60
Purchase #6	$98.80	4.788%	$103.5305	$103.53	$103.55	$103.50
Purchase #7	$245.34	10.194%	$270.35	$270.35	$270.35	$270.40
7 purchase totals =	$1,066.19		$1,158.2780	$1,158.27	$1,158.30	$1,158.40