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	$109.44	3.765%	$113.5604	$113.56	$113.55	$113.60
Purchase #2	$142.75	6.563%	$152.1187	$152.12	$152.10	$152.10
Purchase #3	$80.71	3.643%	$83.6503	$83.65	$83.65	$83.70
Purchase #4	$222.50	9.171%	$242.9055	$242.91	$242.90	$242.90
Purchase #5	$185.29	7.154%	$198.5456	$198.55	$198.55	$198.50
Purchase #6	$114.74	12.273%	$128.822	$128.82	$128.80	$128.80
Purchase #7	$85.84	3.170%	$88.5611	$88.56	$88.55	$88.60
7 purchase totals =	$941.27		$1,008.1636	$1,008.17	$1,008.10	$1,008.20