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	$79.56	4.217%	$82.915	$82.92	$82.90	$82.90
Purchase #2	$208.56	12.798%	$235.2515	$235.25	$235.25	$235.30
Purchase #3	$101.52	12.707%	$114.4201	$114.42	$114.40	$114.40
Purchase #4	$243.85	8.479%	$264.526	$264.53	$264.55	$264.50
Purchase #5	$139.26	7.846%	$150.1863	$150.19	$150.20	$150.20
Purchase #6	$170.69	8.670%	$185.4888	$185.49	$185.50	$185.50
Purchase #7	$83.97	12.608%	$94.5569	$94.56	$94.55	$94.60
7 purchase totals =	$1,027.41		$1,127.3446	$1,127.36	$1,127.35	$1,127.40