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	$181.63	5.376%	$191.3944	$191.39	$191.40	$191.40
Purchase #2	$53.67	10.365%	$59.2329	$59.23	$59.25	$59.20
Purchase #3	$109.78	9.636%	$120.3584	$120.36	$120.35	$120.40
Purchase #4	$133.59	10.251%	$147.2843	$147.28	$147.30	$147.30
Purchase #5	$240.59	9.800%	$264.1678	$264.17	$264.15	$264.20
Purchase #6	$97.39	5.515%	$102.7611	$102.76	$102.75	$102.80
Purchase #7	$60.58	7.859%	$65.341	$65.34	$65.35	$65.30
7 purchase totals =	$877.23		$950.5399	$950.53	$950.55	$950.60