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	$31.49	11.582%	$35.1372	$35.14	$35.15	$35.10
Purchase #2	$52.70	3.196%	$54.3843	$54.38	$54.40	$54.40
Purchase #3	$144.27	3.642%	$149.5243	$149.52	$149.50	$149.50
Purchase #4	$94.47	11.802%	$105.6193	$105.62	$105.60	$105.60
Purchase #5	$245.74	11.397%	$273.747	$273.75	$273.75	$273.70
Purchase #6	$147.75	13.693%	$167.9814	$167.98	$168.00	$168.00
Purchase #7	$226.31	13.570%	$257.0203	$257.02	$257.00	$257.00
7 purchase totals =	$942.73		$1,043.4138	$1,043.41	$1,043.40	$1,043.30