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	$91.96	6.740%	$98.1581	$98.16	$98.15	$98.20
Purchase #2	$215.27	12.605%	$242.4048	$242.40	$242.40	$242.40
Purchase #3	$154.26	8.803%	$167.8395	$167.84	$167.85	$167.80
Purchase #4	$181.65	8.389%	$196.8886	$196.89	$196.90	$196.90
Purchase #5	$69.45	3.635%	$71.9745	$71.97	$71.95	$72.00
Purchase #6	$128.33	9.148%	$140.0696	$140.07	$140.05	$140.10
Purchase #7	$79.31	5.335%	$83.5412	$83.54	$83.55	$83.50
7 purchase totals =	$920.23		$1,000.8763	$1,000.87	$1,000.85	$1,000.90