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	$203.36	10.776%	$225.2741	$225.27	$225.25	$225.30
Purchase #2	$241.50	7.731%	$260.1704	$260.17	$260.15	$260.20
Purchase #3	$64.31	13.331%	$72.8832	$72.88	$72.90	$72.90
Purchase #4	$59.35	4.292%	$61.8973	$61.90	$61.90	$61.90
Purchase #5	$212.26	3.372%	$219.4174	$219.42	$219.40	$219.40
Purchase #6	$218.71	5.107%	$229.8795	$229.88	$229.90	$229.90
Purchase #7	$83.84	3.751%	$86.9848	$86.98	$87.00	$87.00
7 purchase totals =	$1,083.33		$1,156.5067	$1,156.50	$1,156.50	$1,156.60