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	$79.33	5.332%	$83.5599	$83.56	$83.55	$83.60
Purchase #2	$240.41	10.498%	$265.6482	$265.65	$265.65	$265.60
Purchase #3	$236.82	11.170%	$263.2728	$263.27	$263.25	$263.30
Purchase #4	$250.80	4.588%	$262.3067	$262.31	$262.30	$262.30
Purchase #5	$38.69	10.141%	$42.6136	$42.61	$42.60	$42.60
Purchase #6	$119.35	5.860%	$126.3439	$126.34	$126.35	$126.30
Purchase #7	$117.30	4.627%	$122.7275	$122.73	$122.75	$122.70
7 purchase totals =	$1,082.70		$1,166.4726	$1,166.47	$1,166.45	$1,166.40