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	$209.44	6.847%	$223.7804	$223.78	$223.80	$223.80
Purchase #2	$197.64	11.794%	$220.9497	$220.95	$220.95	$220.90
Purchase #3	$153.32	10.152%	$168.885	$168.89	$168.90	$168.90
Purchase #4	$135.61	5.775%	$143.4415	$143.44	$143.45	$143.40
Purchase #5	$103.90	5.131%	$109.2311	$109.23	$109.25	$109.20
Purchase #6	$53.89	7.854%	$58.1225	$58.12	$58.10	$58.10
Purchase #7	$191.73	5.765%	$202.7832	$202.78	$202.80	$202.80
7 purchase totals =	$1,045.53		$1,127.1934	$1,127.19	$1,127.25	$1,127.10