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	$223.29	6.468%	$237.7324	$237.73	$237.75	$237.70
Purchase #2	$40.44	12.566%	$45.5217	$45.52	$45.50	$45.50
Purchase #3	$38.26	6.851%	$40.8812	$40.88	$40.90	$40.90
Purchase #4	$37.72	9.785%	$41.4109	$41.41	$41.40	$41.40
Purchase #5	$66.35	4.144%	$69.0995	$69.10	$69.10	$69.10
Purchase #6	$27.92	12.471%	$31.4019	$31.40	$31.40	$31.40
Purchase #7	$187.50	12.839%	$211.5731	$211.57	$211.55	$211.60
7 purchase totals =	$621.48		$677.6207	$677.61	$677.60	$677.60