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	$69.47	3.360%	$71.8042	$71.80	$71.80	$71.80
Purchase #2	$109.45	4.458%	$114.3293	$114.33	$114.35	$114.30
Purchase #3	$91.53	4.761%	$95.8877	$95.89	$95.90	$95.90
Purchase #4	$250.92	9.597%	$275.0008	$275.00	$275.00	$275.00
Purchase #5	$176.92	6.588%	$188.5755	$188.58	$188.60	$188.60
Purchase #6	$124.76	8.510%	$135.3771	$135.38	$135.40	$135.40
Purchase #7	$127.69	8.469%	$138.5041	$138.50	$138.50	$138.50
7 purchase totals =	$950.74		$1,019.4787	$1,019.48	$1,019.55	$1,019.50