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	$233.76	8.460%	$253.5361	$253.54	$253.55	$253.50
Purchase #2	$182.46	9.808%	$200.3557	$200.36	$200.35	$200.40
Purchase #3	$128.94	12.692%	$145.3051	$145.31	$145.30	$145.30
Purchase #4	$83.55	6.693%	$89.142	$89.14	$89.15	$89.10
Purchase #5	$211.35	7.518%	$227.2393	$227.24	$227.25	$227.20
Purchase #6	$70.66	13.107%	$79.9214	$79.92	$79.90	$79.90
Purchase #7	$178.79	8.785%	$194.4967	$194.50	$194.50	$194.50
7 purchase totals =	$1,089.51		$1,189.9963	$1,190.01	$1,190.00	$1,189.90