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	$104.34	7.662%	$112.3345	$112.33	$112.35	$112.30
Purchase #2	$189.75	4.104%	$197.5373	$197.54	$197.55	$197.50
Purchase #3	$84.96	5.345%	$89.5011	$89.50	$89.50	$89.50
Purchase #4	$171.41	12.637%	$193.0711	$193.07	$193.05	$193.10
Purchase #5	$50.72	5.156%	$53.3351	$53.34	$53.35	$53.30
Purchase #6	$186.26	5.663%	$196.8079	$196.81	$196.80	$196.80
Purchase #7	$58.87	7.453%	$63.2576	$63.26	$63.25	$63.30
7 purchase totals =	$846.31		$905.8446	$905.85	$905.85	$905.80