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	$172.85	9.709%	$189.632	$189.63	$189.65	$189.60
Purchase #2	$13.30	11.526%	$14.833	$14.83	$14.85	$14.80
Purchase #3	$158.61	12.832%	$178.9628	$178.96	$178.95	$179.00
Purchase #4	$54.90	10.397%	$60.608	$60.61	$60.60	$60.60
Purchase #5	$27.46	6.842%	$29.3388	$29.34	$29.35	$29.30
Purchase #6	$191.74	9.459%	$209.8767	$209.88	$209.90	$209.90
Purchase #7	$114.54	11.279%	$127.459	$127.46	$127.45	$127.50
7 purchase totals =	$733.40		$810.7103	$810.71	$810.75	$810.70