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	$160.46	4.629%	$167.8877	$167.89	$167.90	$167.90
Purchase #2	$39.88	4.498%	$41.6738	$41.67	$41.65	$41.70
Purchase #3	$233.96	7.127%	$250.6343	$250.63	$250.65	$250.60
Purchase #4	$229.50	11.142%	$255.0709	$255.07	$255.05	$255.10
Purchase #5	$181.58	10.703%	$201.0145	$201.01	$201.00	$201.00
Purchase #6	$18.36	5.222%	$19.3188	$19.32	$19.30	$19.30
Purchase #7	$153.39	4.314%	$160.0072	$160.01	$160.00	$160.00
7 purchase totals =	$1,017.13		$1,095.6072	$1,095.60	$1,095.55	$1,095.60