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	$100.34	4.819%	$105.1754	$105.18	$105.20	$105.20
Purchase #2	$235.85	7.416%	$253.3406	$253.34	$253.35	$253.30
Purchase #3	$218.60	8.494%	$237.1679	$237.17	$237.15	$237.20
Purchase #4	$62.62	8.387%	$67.8719	$67.87	$67.85	$67.90
Purchase #5	$79.99	11.657%	$89.3144	$89.31	$89.30	$89.30
Purchase #6	$184.92	11.647%	$206.4576	$206.46	$206.45	$206.50
Purchase #7	$199.57	5.229%	$210.0055	$210.01	$210.00	$210.00
7 purchase totals =	$1,081.89		$1,169.3333	$1,169.34	$1,169.30	$1,169.40