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	$90.35	9.640%	$99.0597	$99.06	$99.05	$99.10
Purchase #2	$110.53	4.831%	$115.8697	$115.87	$115.85	$115.90
Purchase #3	$162.74	3.619%	$168.6296	$168.63	$168.65	$168.60
Purchase #4	$215.60	13.753%	$245.2515	$245.25	$245.25	$245.30
Purchase #5	$143.59	6.786%	$153.334	$153.33	$153.35	$153.30
Purchase #6	$91.34	9.140%	$99.6885	$99.69	$99.70	$99.70
Purchase #7	$171.30	8.259%	$185.4477	$185.45	$185.45	$185.40
7 purchase totals =	$985.45		$1,067.2807	$1,067.28	$1,067.30	$1,067.30