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	$183.83	3.346%	$189.981	$189.98	$190.00	$190.00
Purchase #2	$174.85	9.693%	$191.7982	$191.80	$191.80	$191.80
Purchase #3	$156.26	11.753%	$174.6252	$174.63	$174.65	$174.60
Purchase #4	$138.99	9.858%	$152.6916	$152.69	$152.70	$152.70
Purchase #5	$168.30	4.121%	$175.2356	$175.24	$175.25	$175.20
Purchase #6	$102.57	7.168%	$109.9222	$109.92	$109.90	$109.90
Purchase #7	$54.36	4.128%	$56.604	$56.60	$56.60	$56.60
7 purchase totals =	$979.16		$1,050.8578	$1,050.86	$1,050.90	$1,050.80