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	$82.49	4.333%	$86.0643	$86.06	$86.05	$86.10
Purchase #2	$99.76	13.120%	$112.8485	$112.85	$112.85	$112.80
Purchase #3	$157.61	7.764%	$169.8468	$169.85	$169.85	$169.80
Purchase #4	$174.80	6.171%	$185.5869	$185.59	$185.60	$185.60
Purchase #5	$86.44	6.610%	$92.1537	$92.15	$92.15	$92.20
Purchase #6	$200.52	11.417%	$223.4134	$223.41	$223.40	$223.40
Purchase #7	$35.65	7.527%	$38.3334	$38.33	$38.35	$38.30
7 purchase totals =	$837.27		$908.2470	$908.24	$908.25	$908.20