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	$174.57	6.353%	$185.6604	$185.66	$185.65	$185.70
Purchase #2	$54.72	5.145%	$57.5353	$57.54	$57.55	$57.50
Purchase #3	$85.37	13.216%	$96.6525	$96.65	$96.65	$96.70
Purchase #4	$35.69	10.287%	$39.3614	$39.36	$39.35	$39.40
Purchase #5	$133.70	3.740%	$138.7004	$138.70	$138.70	$138.70
Purchase #6	$66.64	8.659%	$72.4104	$72.41	$72.40	$72.40
Purchase #7	$83.79	9.140%	$91.4484	$91.45	$91.45	$91.40
7 purchase totals =	$634.48		$681.7688	$681.77	$681.75	$681.80