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	$51.88	4.206%	$54.0621	$54.06	$54.05	$54.10
Purchase #2	$24.51	7.174%	$26.2683	$26.27	$26.25	$26.30
Purchase #3	$250.81	12.540%	$282.2616	$282.26	$282.25	$282.30
Purchase #4	$86.37	9.280%	$94.3851	$94.39	$94.40	$94.40
Purchase #5	$100.83	4.430%	$105.2968	$105.30	$105.30	$105.30
Purchase #6	$185.82	9.610%	$203.6773	$203.68	$203.70	$203.70
Purchase #7	$229.66	3.752%	$238.2768	$238.28	$238.30	$238.30
7 purchase totals =	$929.88		$1,004.2280	$1,004.24	$1,004.25	$1,004.40