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	$143.90	3.479%	$148.9063	$148.91	$148.90	$148.90
Purchase #2	$49.73	4.552%	$51.9937	$51.99	$52.00	$52.00
Purchase #3	$91.54	8.788%	$99.5845	$99.58	$99.60	$99.60
Purchase #4	$116.96	3.136%	$120.6279	$120.63	$120.65	$120.60
Purchase #5	$135.78	10.860%	$150.5257	$150.53	$150.55	$150.50
Purchase #6	$243.56	6.526%	$259.4547	$259.45	$259.45	$259.50
Purchase #7	$196.81	13.427%	$223.2357	$223.24	$223.25	$223.20
7 purchase totals =	$978.28		$1,054.3285	$1,054.33	$1,054.40	$1,054.30