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	$134.70	11.758%	$150.538	$150.54	$150.55	$150.50
Purchase #2	$127.90	7.399%	$137.3633	$137.36	$137.35	$137.40
Purchase #3	$219.37	8.769%	$238.6066	$238.61	$238.60	$238.60
Purchase #4	$56.55	10.145%	$62.287	$62.29	$62.30	$62.30
Purchase #5	$113.56	6.809%	$121.2923	$121.29	$121.30	$121.30
Purchase #6	$201.62	13.352%	$228.5403	$228.54	$228.55	$228.50
Purchase #7	$196.32	6.304%	$208.696	$208.70	$208.70	$208.70
7 purchase totals =	$1,050.02		$1,147.3235	$1,147.33	$1,147.35	$1,147.30