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	$178.69	9.869%	$196.3249	$196.32	$196.30	$196.30
Purchase #2	$56.90	9.205%	$62.1376	$62.14	$62.15	$62.10
Purchase #3	$45.26	9.703%	$49.6516	$49.65	$49.65	$49.70
Purchase #4	$129.57	7.553%	$139.3564	$139.36	$139.35	$139.40
Purchase #5	$186.93	5.328%	$196.8896	$196.89	$196.90	$196.90
Purchase #6	$30.42	7.362%	$32.6595	$32.66	$32.65	$32.70
Purchase #7	$128.56	6.779%	$137.2751	$137.28	$137.30	$137.30
7 purchase totals =	$756.33		$814.2947	$814.30	$814.30	$814.40