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	$13.42	5.454%	$14.1519	$14.15	$14.15	$14.20
Purchase #2	$49.80	3.641%	$51.6132	$51.61	$51.60	$51.60
Purchase #3	$84.97	6.108%	$90.16	$90.16	$90.15	$90.20
Purchase #4	$228.69	5.164%	$240.4996	$240.50	$240.50	$240.50
Purchase #5	$175.42	3.216%	$181.0615	$181.06	$181.05	$181.10
Purchase #6	$234.98	8.462%	$254.864	$254.86	$254.85	$254.90
Purchase #7	$208.55	10.212%	$229.8471	$229.85	$229.85	$229.80
7 purchase totals =	$995.83		$1,062.1973	$1,062.19	$1,062.15	$1,062.30