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	$245.47	5.584%	$259.177	$259.18	$259.20	$259.20
Purchase #2	$103.69	7.869%	$111.8494	$111.85	$111.85	$111.80
Purchase #3	$96.26	5.679%	$101.7266	$101.73	$101.75	$101.70
Purchase #4	$99.76	9.794%	$109.5305	$109.53	$109.55	$109.50
Purchase #5	$99.91	9.371%	$109.2726	$109.27	$109.25	$109.30
Purchase #6	$55.77	5.584%	$58.8842	$58.88	$58.90	$58.90
Purchase #7	$171.97	4.730%	$180.1042	$180.10	$180.10	$180.10
7 purchase totals =	$872.83		$930.5445	$930.54	$930.60	$930.50