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	$80.58	11.254%	$89.6485	$89.65	$89.65	$89.60
Purchase #2	$190.67	7.405%	$204.7891	$204.79	$204.80	$204.80
Purchase #3	$159.64	8.804%	$173.6947	$173.69	$173.70	$173.70
Purchase #4	$53.86	9.649%	$59.057	$59.06	$59.05	$59.10
Purchase #5	$114.84	11.114%	$127.6033	$127.60	$127.60	$127.60
Purchase #6	$229.90	5.175%	$241.7973	$241.80	$241.80	$241.80
Purchase #7	$202.76	4.609%	$212.1052	$212.11	$212.10	$212.10
7 purchase totals =	$1,032.25		$1,108.6951	$1,108.70	$1,108.70	$1,108.70