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	$99.68	9.860%	$109.5084	$109.51	$109.50	$109.50
Purchase #2	$79.89	12.121%	$89.5735	$89.57	$89.55	$89.60
Purchase #3	$54.90	7.236%	$58.8726	$58.87	$58.85	$58.90
Purchase #4	$57.63	8.352%	$62.4433	$62.44	$62.45	$62.40
Purchase #5	$183.32	12.224%	$205.729	$205.73	$205.75	$205.70
Purchase #6	$115.88	6.328%	$123.2129	$123.21	$123.20	$123.20
Purchase #7	$98.51	5.199%	$103.6315	$103.63	$103.65	$103.60
7 purchase totals =	$689.81		$752.9712	$752.96	$752.95	$752.90