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	$175.40	3.712%	$181.9108	$181.91	$181.90	$181.90
Purchase #2	$116.26	3.225%	$120.0094	$120.01	$120.00	$120.00
Purchase #3	$74.84	10.765%	$82.8965	$82.90	$82.90	$82.90
Purchase #4	$198.76	12.118%	$222.8457	$222.85	$222.85	$222.80
Purchase #5	$152.34	8.683%	$165.5677	$165.57	$165.55	$165.60
Purchase #6	$216.46	11.110%	$240.5087	$240.51	$240.50	$240.50
Purchase #7	$35.89	6.771%	$38.3201	$38.32	$38.30	$38.30
7 purchase totals =	$969.95		$1,052.0589	$1,052.07	$1,052.00	$1,052.00