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	$141.28	13.479%	$160.3231	$160.32	$160.30	$160.30
Purchase #2	$215.39	12.410%	$242.1199	$242.12	$242.10	$242.10
Purchase #3	$192.36	3.770%	$199.612	$199.61	$199.60	$199.60
Purchase #4	$18.27	7.408%	$19.6234	$19.62	$19.60	$19.60
Purchase #5	$75.90	3.370%	$78.4578	$78.46	$78.45	$78.50
Purchase #6	$215.77	3.716%	$223.788	$223.79	$223.80	$223.80
Purchase #7	$242.76	11.454%	$270.5657	$270.57	$270.55	$270.60
7 purchase totals =	$1,101.73		$1,194.4899	$1,194.49	$1,194.40	$1,194.50