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	$41.43	9.418%	$45.3319	$45.33	$45.35	$45.30
Purchase #2	$98.92	10.356%	$109.1642	$109.16	$109.15	$109.20
Purchase #3	$168.29	7.521%	$180.9471	$180.95	$180.95	$180.90
Purchase #4	$216.50	8.804%	$235.5607	$235.56	$235.55	$235.60
Purchase #5	$183.65	10.721%	$203.3391	$203.34	$203.35	$203.30
Purchase #6	$185.92	7.831%	$200.4794	$200.48	$200.50	$200.50
Purchase #7	$51.60	5.328%	$54.3492	$54.35	$54.35	$54.30
7 purchase totals =	$946.31		$1,029.1716	$1,029.17	$1,029.20	$1,029.10