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	$58.52	9.119%	$63.8564	$63.86	$63.85	$63.90
Purchase #2	$211.59	5.229%	$222.654	$222.65	$222.65	$222.70
Purchase #3	$79.68	11.839%	$89.1133	$89.11	$89.10	$89.10
Purchase #4	$175.90	6.532%	$187.3898	$187.39	$187.40	$187.40
Purchase #5	$82.33	12.795%	$92.8641	$92.86	$92.85	$92.90
Purchase #6	$48.27	10.480%	$53.3287	$53.33	$53.35	$53.30
Purchase #7	$76.47	6.397%	$81.3618	$81.36	$81.35	$81.40
7 purchase totals =	$732.76		$790.5681	$790.56	$790.55	$790.70