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	$243.30	13.187%	$275.384	$275.38	$275.40	$275.40
Purchase #2	$54.32	9.625%	$59.5483	$59.55	$59.55	$59.50
Purchase #3	$111.27	6.572%	$118.5827	$118.58	$118.60	$118.60
Purchase #4	$247.53	6.284%	$263.0848	$263.08	$263.10	$263.10
Purchase #5	$72.97	12.873%	$82.3634	$82.36	$82.35	$82.40
Purchase #6	$135.99	8.728%	$147.8592	$147.86	$147.85	$147.90
Purchase #7	$103.76	5.157%	$109.1109	$109.11	$109.10	$109.10
7 purchase totals =	$969.14		$1,055.9333	$1,055.92	$1,055.95	$1,056.00