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	$187.64	11.819%	$209.8172	$209.82	$209.80	$209.80
Purchase #2	$176.81	3.816%	$183.5571	$183.56	$183.55	$183.60
Purchase #3	$155.65	12.632%	$175.3117	$175.31	$175.30	$175.30
Purchase #4	$104.96	10.219%	$115.6859	$115.69	$115.70	$115.70
Purchase #5	$171.96	9.729%	$188.69	$188.69	$188.70	$188.70
Purchase #6	$48.67	11.242%	$54.1415	$54.14	$54.15	$54.10
Purchase #7	$185.80	5.694%	$196.3795	$196.38	$196.40	$196.40
7 purchase totals =	$1,031.49		$1,123.5829	$1,123.59	$1,123.60	$1,123.60