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	$201.58	10.562%	$222.8709	$222.87	$222.85	$222.90
Purchase #2	$80.35	11.160%	$89.3171	$89.32	$89.30	$89.30
Purchase #3	$245.76	6.658%	$262.1227	$262.12	$262.10	$262.10
Purchase #4	$145.32	13.134%	$164.4063	$164.41	$164.40	$164.40
Purchase #5	$250.93	3.635%	$260.0513	$260.05	$260.05	$260.10
Purchase #6	$62.32	13.529%	$70.7513	$70.75	$70.75	$70.80
Purchase #7	$139.92	5.793%	$148.0256	$148.03	$148.05	$148.00
7 purchase totals =	$1,126.18		$1,217.5452	$1,217.55	$1,217.50	$1,217.60