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	$43.79	5.702%	$46.2869	$46.29	$46.30	$46.30
Purchase #2	$43.86	4.549%	$45.8552	$45.86	$45.85	$45.90
Purchase #3	$175.94	9.837%	$193.2472	$193.25	$193.25	$193.20
Purchase #4	$243.42	12.254%	$273.2487	$273.25	$273.25	$273.20
Purchase #5	$99.43	6.268%	$105.6623	$105.66	$105.65	$105.70
Purchase #6	$219.99	3.423%	$227.5203	$227.52	$227.50	$227.50
Purchase #7	$160.37	3.476%	$165.9445	$165.94	$165.95	$165.90
7 purchase totals =	$986.80		$1,057.7651	$1,057.77	$1,057.75	$1,057.70