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	$167.75	10.662%	$185.6355	$185.64	$185.65	$185.60
Purchase #2	$98.74	12.761%	$111.3402	$111.34	$111.35	$111.30
Purchase #3	$241.63	13.274%	$273.704	$273.70	$273.70	$273.70
Purchase #4	$33.34	7.133%	$35.7181	$35.72	$35.70	$35.70
Purchase #5	$125.77	4.134%	$130.9693	$130.97	$130.95	$131.00
Purchase #6	$211.75	12.523%	$238.2675	$238.27	$238.25	$238.30
Purchase #7	$196.53	9.569%	$215.336	$215.34	$215.35	$215.30
7 purchase totals =	$1,075.51		$1,190.9706	$1,190.98	$1,190.95	$1,190.90