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	$84.31	8.590%	$91.5522	$91.55	$91.55	$91.60
Purchase #2	$52.98	6.233%	$56.2822	$56.28	$56.30	$56.30
Purchase #3	$165.63	9.549%	$181.446	$181.45	$181.45	$181.40
Purchase #4	$99.96	9.228%	$109.1843	$109.18	$109.20	$109.20
Purchase #5	$239.28	10.437%	$264.2537	$264.25	$264.25	$264.30
Purchase #6	$143.37	3.549%	$148.4582	$148.46	$148.45	$148.50
Purchase #7	$250.38	12.674%	$282.1132	$282.11	$282.10	$282.10
7 purchase totals =	$1,035.91		$1,133.2898	$1,133.28	$1,133.30	$1,133.40