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	$147.50	9.187%	$161.0508	$161.05	$161.05	$161.10
Purchase #2	$155.61	3.784%	$161.4983	$161.50	$161.50	$161.50
Purchase #3	$102.56	6.461%	$109.1864	$109.19	$109.20	$109.20
Purchase #4	$186.96	5.245%	$196.7661	$196.77	$196.75	$196.80
Purchase #5	$83.45	7.499%	$89.7079	$89.71	$89.70	$89.70
Purchase #6	$88.30	3.824%	$91.6766	$91.68	$91.70	$91.70
Purchase #7	$149.91	8.402%	$162.5054	$162.51	$162.50	$162.50
7 purchase totals =	$914.29		$972.3915	$972.41	$972.40	$972.50