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	$67.78	6.425%	$72.1349	$72.13	$72.15	$72.10
Purchase #2	$161.27	4.506%	$168.5368	$168.54	$168.55	$168.50
Purchase #3	$245.80	6.846%	$262.6275	$262.63	$262.65	$262.60
Purchase #4	$26.43	11.663%	$29.5125	$29.51	$29.50	$29.50
Purchase #5	$148.88	12.454%	$167.4215	$167.42	$167.40	$167.40
Purchase #6	$169.98	5.322%	$179.0263	$179.03	$179.05	$179.00
Purchase #7	$249.88	9.373%	$273.3013	$273.30	$273.30	$273.30
7 purchase totals =	$1,070.02		$1,152.5608	$1,152.56	$1,152.60	$1,152.40