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	$101.53	10.459%	$112.149	$112.15	$112.15	$112.10
Purchase #2	$167.72	10.361%	$185.0975	$185.10	$185.10	$185.10
Purchase #3	$201.48	10.643%	$222.9235	$222.92	$222.90	$222.90
Purchase #4	$148.31	13.512%	$168.3496	$168.35	$168.35	$168.30
Purchase #5	$91.87	7.366%	$98.6371	$98.64	$98.65	$98.60
Purchase #6	$214.49	12.741%	$241.8182	$241.82	$241.80	$241.80
Purchase #7	$99.61	3.461%	$103.0575	$103.06	$103.05	$103.10
7 purchase totals =	$1,025.01		$1,132.0324	$1,132.04	$1,132.00	$1,131.90