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	$175.27	4.120%	$182.4911	$182.49	$182.50	$182.50
Purchase #2	$124.79	4.811%	$130.7936	$130.79	$130.80	$130.80
Purchase #3	$163.40	6.627%	$174.2285	$174.23	$174.25	$174.20
Purchase #4	$231.92	10.287%	$255.7776	$255.78	$255.80	$255.80
Purchase #5	$75.50	9.728%	$82.8446	$82.84	$82.85	$82.80
Purchase #6	$89.55	11.736%	$100.0596	$100.06	$100.05	$100.10
Purchase #7	$158.33	11.595%	$176.6884	$176.69	$176.70	$176.70
7 purchase totals =	$1,018.76		$1,102.8834	$1,102.88	$1,102.95	$1,102.90