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	$250.62	7.559%	$269.5644	$269.56	$269.55	$269.60
Purchase #2	$149.46	12.458%	$168.0797	$168.08	$168.10	$168.10
Purchase #3	$116.49	9.201%	$127.2082	$127.21	$127.20	$127.20
Purchase #4	$126.51	12.166%	$141.9012	$141.90	$141.90	$141.90
Purchase #5	$82.56	5.453%	$87.062	$87.06	$87.05	$87.10
Purchase #6	$160.36	3.365%	$165.7561	$165.76	$165.75	$165.80
Purchase #7	$92.68	11.298%	$103.151	$103.15	$103.15	$103.20
7 purchase totals =	$978.68		$1,062.7226	$1,062.72	$1,062.70	$1,062.90