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	$164.85	5.242%	$173.4914	$173.49	$173.50	$173.50
Purchase #2	$95.48	3.112%	$98.4513	$98.45	$98.45	$98.50
Purchase #3	$123.31	3.332%	$127.4187	$127.42	$127.40	$127.40
Purchase #4	$193.27	11.153%	$214.8254	$214.83	$214.85	$214.80
Purchase #5	$41.83	6.486%	$44.5431	$44.54	$44.55	$44.50
Purchase #6	$223.30	11.661%	$249.339	$249.34	$249.35	$249.30
Purchase #7	$135.56	9.401%	$148.304	$148.30	$148.30	$148.30
7 purchase totals =	$977.60		$1,056.3729	$1,056.37	$1,056.40	$1,056.30