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	$109.59	13.107%	$123.954	$123.95	$123.95	$124.00
Purchase #2	$141.56	10.539%	$156.479	$156.48	$156.50	$156.50
Purchase #3	$12.73	12.403%	$14.3089	$14.31	$14.30	$14.30
Purchase #4	$127.71	13.737%	$145.2535	$145.25	$145.25	$145.30
Purchase #5	$95.99	3.139%	$99.0031	$99.00	$99.00	$99.00
Purchase #6	$148.44	9.123%	$161.9822	$161.98	$162.00	$162.00
Purchase #7	$30.87	6.362%	$32.8339	$32.83	$32.85	$32.80
7 purchase totals =	$666.89		$733.8146	$733.80	$733.85	$733.90