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	$168.69	7.163%	$180.7733	$180.77	$180.75	$180.80
Purchase #2	$96.27	4.601%	$100.6994	$100.70	$100.70	$100.70
Purchase #3	$245.91	9.124%	$268.3468	$268.35	$268.35	$268.30
Purchase #4	$139.45	6.538%	$148.5672	$148.57	$148.55	$148.60
Purchase #5	$242.85	4.582%	$253.9774	$253.98	$254.00	$254.00
Purchase #6	$49.29	4.417%	$51.4671	$51.47	$51.45	$51.50
Purchase #7	$70.60	3.237%	$72.8853	$72.89	$72.90	$72.90
7 purchase totals =	$1,013.06		$1,076.7165	$1,076.73	$1,076.70	$1,076.80