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	$189.62	12.285%	$212.9148	$212.91	$212.90	$212.90
Purchase #2	$87.85	10.154%	$96.7703	$96.77	$96.75	$96.80
Purchase #3	$52.90	3.387%	$54.6917	$54.69	$54.70	$54.70
Purchase #4	$218.85	10.701%	$242.2691	$242.27	$242.25	$242.30
Purchase #5	$82.30	9.399%	$90.0354	$90.04	$90.05	$90.00
Purchase #6	$149.39	6.558%	$159.187	$159.19	$159.20	$159.20
Purchase #7	$181.42	8.465%	$196.7772	$196.78	$196.80	$196.80
7 purchase totals =	$962.33		$1,052.6455	$1,052.65	$1,052.65	$1,052.70