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	$137.59	5.645%	$145.357	$145.36	$145.35	$145.40
Purchase #2	$137.35	9.419%	$150.287	$150.29	$150.30	$150.30
Purchase #3	$170.69	8.568%	$185.3147	$185.31	$185.30	$185.30
Purchase #4	$101.96	3.519%	$105.548	$105.55	$105.55	$105.50
Purchase #5	$249.90	7.310%	$268.1677	$268.17	$268.15	$268.20
Purchase #6	$77.37	7.182%	$82.9267	$82.93	$82.95	$82.90
Purchase #7	$190.97	8.548%	$207.2941	$207.29	$207.30	$207.30
7 purchase totals =	$1,065.83		$1,144.8952	$1,144.90	$1,144.90	$1,144.90