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	$217.78	3.489%	$225.3783	$225.38	$225.40	$225.40
Purchase #2	$92.67	4.445%	$96.7892	$96.79	$96.80	$96.80
Purchase #3	$229.33	13.426%	$260.1198	$260.12	$260.10	$260.10
Purchase #4	$179.28	8.667%	$194.8182	$194.82	$194.80	$194.80
Purchase #5	$103.97	13.577%	$118.086	$118.09	$118.10	$118.10
Purchase #6	$55.77	6.118%	$59.182	$59.18	$59.20	$59.20
Purchase #7	$51.32	13.871%	$58.4386	$58.44	$58.45	$58.40
7 purchase totals =	$930.12		$1,012.8121	$1,012.82	$1,012.85	$1,012.80