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	$145.29	9.748%	$159.4529	$159.45	$159.45	$159.50
Purchase #2	$175.46	9.163%	$191.5374	$191.54	$191.55	$191.50
Purchase #3	$182.27	6.830%	$194.719	$194.72	$194.70	$194.70
Purchase #4	$78.28	4.720%	$81.9748	$81.97	$81.95	$82.00
Purchase #5	$45.53	8.140%	$49.2361	$49.24	$49.25	$49.20
Purchase #6	$96.53	3.456%	$99.8661	$99.87	$99.85	$99.90
Purchase #7	$45.87	3.304%	$47.3855	$47.39	$47.40	$47.40
7 purchase totals =	$769.23		$824.1718	$824.18	$824.15	$824.20