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	$156.53	10.817%	$173.4619	$173.46	$173.45	$173.50
Purchase #2	$180.27	6.430%	$191.8614	$191.86	$191.85	$191.90
Purchase #3	$184.33	13.581%	$209.3639	$209.36	$209.35	$209.40
Purchase #4	$8.36	11.143%	$9.2916	$9.29	$9.30	$9.30
Purchase #5	$49.72	8.172%	$53.7831	$53.78	$53.80	$53.80
Purchase #6	$50.37	8.376%	$54.589	$54.59	$54.60	$54.60
Purchase #7	$81.38	11.241%	$90.5279	$90.53	$90.55	$90.50
7 purchase totals =	$710.96		$782.8788	$782.87	$782.90	$783.00