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	$106.62	8.511%	$115.6944	$115.69	$115.70	$115.70
Purchase #2	$83.43	9.593%	$91.4334	$91.43	$91.45	$91.40
Purchase #3	$240.38	9.677%	$263.6416	$263.64	$263.65	$263.60
Purchase #4	$153.81	13.512%	$174.5928	$174.59	$174.60	$174.60
Purchase #5	$172.36	7.334%	$185.0009	$185.00	$185.00	$185.00
Purchase #6	$59.57	9.860%	$65.4436	$65.44	$65.45	$65.40
Purchase #7	$164.55	12.417%	$184.9822	$184.98	$185.00	$185.00
7 purchase totals =	$980.72		$1,080.7889	$1,080.77	$1,080.85	$1,080.70