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	$76.56	3.494%	$79.235	$79.24	$79.25	$79.20
Purchase #2	$249.46	9.563%	$273.3159	$273.32	$273.30	$273.30
Purchase #3	$41.45	7.667%	$44.628	$44.63	$44.65	$44.60
Purchase #4	$247.50	3.800%	$256.905	$256.91	$256.90	$256.90
Purchase #5	$71.99	13.653%	$81.8188	$81.82	$81.80	$81.80
Purchase #6	$145.77	13.610%	$165.6093	$165.61	$165.60	$165.60
Purchase #7	$181.38	4.495%	$189.533	$189.53	$189.55	$189.50
7 purchase totals =	$1,014.11		$1,091.0450	$1,091.06	$1,091.05	$1,090.90