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	$215.42	3.765%	$223.5306	$223.53	$223.55	$223.50
Purchase #2	$33.28	5.178%	$35.0032	$35.00	$35.00	$35.00
Purchase #3	$68.51	10.675%	$75.8234	$75.82	$75.80	$75.80
Purchase #4	$203.31	3.474%	$210.373	$210.37	$210.35	$210.40
Purchase #5	$191.60	10.663%	$212.0303	$212.03	$212.05	$212.00
Purchase #6	$35.75	5.320%	$37.6519	$37.65	$37.65	$37.70
Purchase #7	$166.69	10.685%	$184.5008	$184.50	$184.50	$184.50
7 purchase totals =	$914.56		$978.9132	$978.90	$978.90	$978.90