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	$88.56	7.545%	$95.2419	$95.24	$95.25	$95.20
Purchase #2	$127.57	10.621%	$141.1192	$141.12	$141.10	$141.10
Purchase #3	$149.32	13.121%	$168.9123	$168.91	$168.90	$168.90
Purchase #4	$249.89	8.369%	$270.8033	$270.80	$270.80	$270.80
Purchase #5	$93.64	7.685%	$100.8362	$100.84	$100.85	$100.80
Purchase #6	$227.51	9.445%	$248.9983	$249.00	$249.00	$249.00
Purchase #7	$28.36	10.802%	$31.4234	$31.42	$31.40	$31.40
7 purchase totals =	$964.85		$1,057.3346	$1,057.33	$1,057.30	$1,057.20