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	$94.49	5.421%	$99.6123	$99.61	$99.60	$99.60
Purchase #2	$100.49	12.844%	$113.3969	$113.40	$113.40	$113.40
Purchase #3	$198.30	10.343%	$218.8102	$218.81	$218.80	$218.80
Purchase #4	$170.55	12.212%	$191.3776	$191.38	$191.40	$191.40
Purchase #5	$19.97	6.636%	$21.2952	$21.30	$21.30	$21.30
Purchase #6	$241.96	7.427%	$259.9304	$259.93	$259.95	$259.90
Purchase #7	$114.76	5.333%	$120.8802	$120.88	$120.90	$120.90
7 purchase totals =	$940.52		$1,025.3028	$1,025.31	$1,025.35	$1,025.30