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	$49.80	10.228%	$54.8935	$54.89	$54.90	$54.90
Purchase #2	$238.35	10.369%	$263.0645	$263.06	$263.05	$263.10
Purchase #3	$77.79	11.585%	$86.802	$86.80	$86.80	$86.80
Purchase #4	$169.46	6.630%	$180.6952	$180.70	$180.70	$180.70
Purchase #5	$183.89	6.717%	$196.2419	$196.24	$196.25	$196.20
Purchase #6	$59.92	5.171%	$63.0185	$63.02	$63.00	$63.00
Purchase #7	$245.56	7.404%	$263.7413	$263.74	$263.75	$263.70
7 purchase totals =	$1,024.77		$1,108.4569	$1,108.45	$1,108.45	$1,108.40