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	$178.45	10.148%	$196.5591	$196.56	$196.55	$196.60
Purchase #2	$240.85	3.498%	$249.2749	$249.27	$249.25	$249.30
Purchase #3	$99.25	10.628%	$109.7983	$109.80	$109.80	$109.80
Purchase #4	$17.38	11.757%	$19.4234	$19.42	$19.40	$19.40
Purchase #5	$128.63	10.118%	$141.6448	$141.64	$141.65	$141.60
Purchase #6	$217.65	10.467%	$240.4314	$240.43	$240.45	$240.40
Purchase #7	$127.65	13.130%	$144.4104	$144.41	$144.40	$144.40
7 purchase totals =	$1,009.86		$1,101.5423	$1,101.53	$1,101.50	$1,101.50