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	$192.54	3.285%	$198.8649	$198.86	$198.85	$198.90
Purchase #2	$158.64	13.635%	$180.2706	$180.27	$180.25	$180.30
Purchase #3	$22.42	8.781%	$24.3887	$24.39	$24.40	$24.40
Purchase #4	$232.34	13.837%	$264.4889	$264.49	$264.50	$264.50
Purchase #5	$148.83	10.432%	$164.3559	$164.36	$164.35	$164.40
Purchase #6	$213.64	9.390%	$233.7008	$233.70	$233.70	$233.70
Purchase #7	$35.88	4.485%	$37.4892	$37.49	$37.50	$37.50
7 purchase totals =	$1,004.29		$1,103.5590	$1,103.56	$1,103.55	$1,103.70