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	$99.65	3.433%	$103.071	$103.07	$103.05	$103.10
Purchase #2	$210.89	13.211%	$238.7507	$238.75	$238.75	$238.80
Purchase #3	$142.62	9.647%	$156.3786	$156.38	$156.40	$156.40
Purchase #4	$82.60	4.450%	$86.2757	$86.28	$86.30	$86.30
Purchase #5	$245.93	3.146%	$253.667	$253.67	$253.65	$253.70
Purchase #6	$123.82	3.374%	$127.9977	$128.00	$128.00	$128.00
Purchase #7	$167.73	7.173%	$179.7613	$179.76	$179.75	$179.80
7 purchase totals =	$1,073.24		$1,145.9020	$1,145.91	$1,145.90	$1,146.10