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	$81.88	4.586%	$85.635	$85.64	$85.65	$85.60
Purchase #2	$250.81	4.689%	$262.5705	$262.57	$262.55	$262.60
Purchase #3	$162.68	3.103%	$167.728	$167.73	$167.75	$167.70
Purchase #4	$75.91	4.589%	$79.3935	$79.39	$79.40	$79.40
Purchase #5	$224.85	9.173%	$245.4755	$245.48	$245.50	$245.50
Purchase #6	$96.78	3.698%	$100.3589	$100.36	$100.35	$100.40
Purchase #7	$41.39	10.381%	$45.6867	$45.69	$45.70	$45.70
7 purchase totals =	$934.30		$986.8481	$986.86	$986.90	$986.90