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	$221.66	6.166%	$235.3276	$235.33	$235.35	$235.30
Purchase #2	$237.25	7.854%	$255.8836	$255.88	$255.90	$255.90
Purchase #3	$99.72	3.863%	$103.5722	$103.57	$103.55	$103.60
Purchase #4	$134.30	7.306%	$144.112	$144.11	$144.10	$144.10
Purchase #5	$77.33	4.343%	$80.6884	$80.69	$80.70	$80.70
Purchase #6	$215.78	3.348%	$223.0043	$223.00	$223.00	$223.00
Purchase #7	$168.43	6.736%	$179.7754	$179.78	$179.80	$179.80
7 purchase totals =	$1,154.47		$1,222.3635	$1,222.36	$1,222.40	$1,222.40