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	$140.68	9.307%	$153.7731	$153.77	$153.75	$153.80
Purchase #2	$53.61	10.123%	$59.0369	$59.04	$59.05	$59.00
Purchase #3	$49.87	13.588%	$56.6463	$56.65	$56.65	$56.60
Purchase #4	$99.85	4.731%	$104.5739	$104.57	$104.55	$104.60
Purchase #5	$196.53	5.108%	$206.5688	$206.57	$206.55	$206.60
Purchase #6	$80.50	13.739%	$91.5599	$91.56	$91.55	$91.60
Purchase #7	$162.61	6.741%	$173.5715	$173.57	$173.55	$173.60
7 purchase totals =	$783.65		$845.7304	$845.73	$845.65	$845.80