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	$88.38	6.622%	$94.2325	$94.23	$94.25	$94.20
Purchase #2	$94.49	12.789%	$106.5743	$106.57	$106.55	$106.60
Purchase #3	$85.27	4.815%	$89.3758	$89.38	$89.40	$89.40
Purchase #4	$79.57	7.613%	$85.6277	$85.63	$85.65	$85.60
Purchase #5	$202.30	7.183%	$216.8312	$216.83	$216.85	$216.80
Purchase #6	$196.29	7.854%	$211.7066	$211.71	$211.70	$211.70
Purchase #7	$189.68	12.455%	$213.3046	$213.30	$213.30	$213.30
7 purchase totals =	$935.98		$1,017.6527	$1,017.65	$1,017.70	$1,017.60