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	$92.29	13.147%	$104.4234	$104.42	$104.40	$104.40
Purchase #2	$29.25	3.518%	$30.279	$30.28	$30.30	$30.30
Purchase #3	$106.74	4.102%	$111.1185	$111.12	$111.10	$111.10
Purchase #4	$78.59	3.630%	$81.4428	$81.44	$81.45	$81.40
Purchase #5	$212.61	5.211%	$223.6891	$223.69	$223.70	$223.70
Purchase #6	$170.72	8.865%	$185.8543	$185.85	$185.85	$185.90
Purchase #7	$43.66	6.498%	$46.497	$46.50	$46.50	$46.50
7 purchase totals =	$733.86		$783.3041	$783.30	$783.30	$783.30