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	$123.95	7.251%	$132.9376	$132.94	$132.95	$132.90
Purchase #2	$241.81	9.229%	$264.1266	$264.13	$264.15	$264.10
Purchase #3	$79.62	7.285%	$85.4203	$85.42	$85.40	$85.40
Purchase #4	$5.59	12.647%	$6.297	$6.30	$6.30	$6.30
Purchase #5	$225.73	10.506%	$249.4452	$249.45	$249.45	$249.40
Purchase #6	$166.41	10.514%	$183.9063	$183.91	$183.90	$183.90
Purchase #7	$215.72	11.367%	$240.2409	$240.24	$240.25	$240.20
7 purchase totals =	$1,058.83		$1,162.3739	$1,162.39	$1,162.40	$1,162.20