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	$92.61	5.781%	$97.9638	$97.96	$97.95	$98.00
Purchase #2	$220.60	8.809%	$240.0327	$240.03	$240.05	$240.00
Purchase #3	$78.52	6.479%	$83.6073	$83.61	$83.60	$83.60
Purchase #4	$104.98	10.420%	$115.9189	$115.92	$115.90	$115.90
Purchase #5	$77.56	5.196%	$81.59	$81.59	$81.60	$81.60
Purchase #6	$143.57	5.765%	$151.8468	$151.85	$151.85	$151.80
Purchase #7	$76.93	8.417%	$83.4052	$83.41	$83.40	$83.40
7 purchase totals =	$794.77		$854.3647	$854.37	$854.35	$854.30