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	$185.93	5.574%	$196.2937	$196.29	$196.30	$196.30
Purchase #2	$6.62	12.176%	$7.4261	$7.43	$7.45	$7.40
Purchase #3	$45.26	6.432%	$48.1711	$48.17	$48.15	$48.20
Purchase #4	$21.59	3.653%	$22.3787	$22.38	$22.40	$22.40
Purchase #5	$119.27	3.708%	$123.6925	$123.69	$123.70	$123.70
Purchase #6	$104.61	4.242%	$109.0476	$109.05	$109.05	$109.00
Purchase #7	$71.65	12.379%	$80.5196	$80.52	$80.50	$80.50
7 purchase totals =	$554.93		$587.5293	$587.53	$587.55	$587.50