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	$150.84	5.410%	$159.0004	$159.00	$159.00	$159.00
Purchase #2	$140.34	7.639%	$151.0606	$151.06	$151.05	$151.10
Purchase #3	$162.58	11.395%	$181.106	$181.11	$181.10	$181.10
Purchase #4	$73.47	6.826%	$78.4851	$78.49	$78.50	$78.50
Purchase #5	$25.48	5.135%	$26.7884	$26.79	$26.80	$26.80
Purchase #6	$99.99	5.104%	$105.0935	$105.09	$105.10	$105.10
Purchase #7	$40.81	12.476%	$45.9015	$45.90	$45.90	$45.90
7 purchase totals =	$693.51		$747.4355	$747.44	$747.45	$747.50