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	$123.59	10.740%	$136.8636	$136.86	$136.85	$136.90
Purchase #2	$214.86	3.157%	$221.6431	$221.64	$221.65	$221.60
Purchase #3	$54.60	9.407%	$59.7362	$59.74	$59.75	$59.70
Purchase #4	$135.31	12.808%	$152.6405	$152.64	$152.65	$152.60
Purchase #5	$85.56	6.358%	$90.9999	$91.00	$91.00	$91.00
Purchase #6	$216.85	7.457%	$233.0205	$233.02	$233.00	$233.00
Purchase #7	$185.97	12.503%	$209.2218	$209.22	$209.20	$209.20
7 purchase totals =	$1,016.74		$1,104.1256	$1,104.12	$1,104.10	$1,104.00