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	$241.55	13.870%	$275.053	$275.05	$275.05	$275.10
Purchase #2	$219.88	11.120%	$244.3307	$244.33	$244.35	$244.30
Purchase #3	$86.95	9.798%	$95.4694	$95.47	$95.45	$95.50
Purchase #4	$91.53	8.219%	$99.0529	$99.05	$99.05	$99.10
Purchase #5	$167.56	7.849%	$180.7118	$180.71	$180.70	$180.70
Purchase #6	$123.74	13.432%	$140.3608	$140.36	$140.35	$140.40
Purchase #7	$58.76	5.424%	$61.9471	$61.95	$61.95	$61.90
7 purchase totals =	$989.97		$1,096.9257	$1,096.92	$1,096.90	$1,097.00