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	$19.75	12.315%	$22.1822	$22.18	$22.20	$22.20
Purchase #2	$47.83	11.864%	$53.5046	$53.50	$53.50	$53.50
Purchase #3	$54.27	9.373%	$59.3567	$59.36	$59.35	$59.40
Purchase #4	$196.98	9.233%	$215.1672	$215.17	$215.15	$215.20
Purchase #5	$174.87	5.349%	$184.2238	$184.22	$184.20	$184.20
Purchase #6	$132.83	11.280%	$147.8132	$147.81	$147.80	$147.80
Purchase #7	$129.39	10.492%	$142.9656	$142.97	$142.95	$143.00
7 purchase totals =	$755.92		$825.2133	$825.21	$825.15	$825.30