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	$250.39	8.376%	$271.3627	$271.36	$271.35	$271.40
Purchase #2	$89.50	7.623%	$96.3226	$96.32	$96.30	$96.30
Purchase #3	$79.43	6.849%	$84.8702	$84.87	$84.85	$84.90
Purchase #4	$185.70	10.364%	$204.9459	$204.95	$204.95	$204.90
Purchase #5	$41.82	7.723%	$45.0498	$45.05	$45.05	$45.00
Purchase #6	$55.25	7.292%	$59.2788	$59.28	$59.30	$59.30
Purchase #7	$220.80	8.460%	$239.4797	$239.48	$239.50	$239.50
7 purchase totals =	$922.89		$1,001.3097	$1,001.31	$1,001.30	$1,001.30