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	$103.61	10.212%	$114.1907	$114.19	$114.20	$114.20
Purchase #2	$229.70	4.595%	$240.2547	$240.25	$240.25	$240.30
Purchase #3	$85.97	10.649%	$95.1249	$95.12	$95.10	$95.10
Purchase #4	$58.84	5.635%	$62.1556	$62.16	$62.15	$62.20
Purchase #5	$105.76	3.268%	$109.2162	$109.22	$109.20	$109.20
Purchase #6	$81.96	10.252%	$90.3625	$90.36	$90.35	$90.40
Purchase #7	$182.52	7.405%	$196.0356	$196.04	$196.05	$196.00
7 purchase totals =	$848.36		$907.3402	$907.34	$907.30	$907.40