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	$52.59	7.171%	$56.3612	$56.36	$56.35	$56.40
Purchase #2	$196.82	13.747%	$223.8768	$223.88	$223.90	$223.90
Purchase #3	$98.45	9.180%	$107.4877	$107.49	$107.50	$107.50
Purchase #4	$231.55	13.771%	$263.4368	$263.44	$263.45	$263.40
Purchase #5	$166.77	13.271%	$188.902	$188.90	$188.90	$188.90
Purchase #6	$28.43	11.370%	$31.6625	$31.66	$31.65	$31.70
Purchase #7	$249.26	4.183%	$259.6865	$259.69	$259.70	$259.70
7 purchase totals =	$1,023.87		$1,131.4135	$1,131.42	$1,131.45	$1,131.50