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	$42.37	12.174%	$47.5281	$47.53	$47.55	$47.50
Purchase #2	$196.86	9.568%	$215.6956	$215.70	$215.70	$215.70
Purchase #3	$143.36	13.125%	$162.176	$162.18	$162.20	$162.20
Purchase #4	$97.71	5.245%	$102.8349	$102.83	$102.85	$102.80
Purchase #5	$35.31	13.609%	$40.1153	$40.12	$40.10	$40.10
Purchase #6	$180.64	8.865%	$196.6537	$196.65	$196.65	$196.70
Purchase #7	$159.30	5.108%	$167.437	$167.44	$167.45	$167.40
7 purchase totals =	$855.55		$932.4406	$932.45	$932.50	$932.40