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	$182.48	8.537%	$198.0583	$198.06	$198.05	$198.10
Purchase #2	$204.32	11.316%	$227.4409	$227.44	$227.45	$227.40
Purchase #3	$30.66	4.418%	$32.0146	$32.01	$32.00	$32.00
Purchase #4	$139.54	5.485%	$147.1938	$147.19	$147.20	$147.20
Purchase #5	$81.54	12.301%	$91.5702	$91.57	$91.55	$91.60
Purchase #6	$162.41	5.422%	$171.2159	$171.22	$171.20	$171.20
Purchase #7	$218.32	3.208%	$225.3237	$225.32	$225.30	$225.30
7 purchase totals =	$1,019.27		$1,092.8174	$1,092.81	$1,092.75	$1,092.80