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	$209.46	13.175%	$237.0564	$237.06	$237.05	$237.10
Purchase #2	$77.56	6.719%	$82.7713	$82.77	$82.75	$82.80
Purchase #3	$144.80	9.739%	$158.9021	$158.90	$158.90	$158.90
Purchase #4	$178.74	13.713%	$203.2506	$203.25	$203.25	$203.30
Purchase #5	$18.73	5.633%	$19.7851	$19.79	$19.80	$19.80
Purchase #6	$159.38	7.658%	$171.5853	$171.59	$171.60	$171.60
Purchase #7	$209.61	9.654%	$229.8457	$229.85	$229.85	$229.80
7 purchase totals =	$998.28		$1,103.1965	$1,103.21	$1,103.20	$1,103.30