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	$137.87	3.263%	$142.3687	$142.37	$142.35	$142.40
Purchase #2	$142.50	13.721%	$162.0524	$162.05	$162.05	$162.10
Purchase #3	$250.71	12.732%	$282.6304	$282.63	$282.65	$282.60
Purchase #4	$196.31	11.674%	$219.2272	$219.23	$219.25	$219.20
Purchase #5	$78.34	8.580%	$85.0616	$85.06	$85.05	$85.10
Purchase #6	$28.52	9.739%	$31.2976	$31.30	$31.30	$31.30
Purchase #7	$128.40	7.579%	$138.1314	$138.13	$138.15	$138.10
7 purchase totals =	$962.65		$1,060.7693	$1,060.77	$1,060.80	$1,060.80