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	$194.91	7.697%	$209.9122	$209.91	$209.90	$209.90
Purchase #2	$46.90	13.200%	$53.0908	$53.09	$53.10	$53.10
Purchase #3	$174.92	12.309%	$196.4509	$196.45	$196.45	$196.50
Purchase #4	$76.55	10.802%	$84.8189	$84.82	$84.80	$84.80
Purchase #5	$25.80	4.687%	$27.0092	$27.01	$27.00	$27.00
Purchase #6	$85.81	6.220%	$91.1474	$91.15	$91.15	$91.10
Purchase #7	$100.56	13.261%	$113.8953	$113.90	$113.90	$113.90
7 purchase totals =	$705.45		$776.3247	$776.33	$776.30	$776.30