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	$98.92	5.602%	$104.4615	$104.46	$104.45	$104.50
Purchase #2	$175.98	5.646%	$185.9158	$185.92	$185.90	$185.90
Purchase #3	$110.43	4.437%	$115.3298	$115.33	$115.35	$115.30
Purchase #4	$118.57	9.784%	$130.1709	$130.17	$130.15	$130.20
Purchase #5	$152.54	5.290%	$160.6094	$160.61	$160.60	$160.60
Purchase #6	$54.76	13.527%	$62.1674	$62.17	$62.15	$62.20
Purchase #7	$179.71	6.199%	$190.8502	$190.85	$190.85	$190.90
7 purchase totals =	$890.91		$949.5050	$949.51	$949.45	$949.60