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	$142.66	6.601%	$152.077	$152.08	$152.10	$152.10
Purchase #2	$25.65	5.555%	$27.0749	$27.07	$27.05	$27.10
Purchase #3	$238.89	4.774%	$250.2946	$250.29	$250.30	$250.30
Purchase #4	$220.69	13.693%	$250.9091	$250.91	$250.90	$250.90
Purchase #5	$224.36	8.539%	$243.5181	$243.52	$243.50	$243.50
Purchase #6	$79.51	9.117%	$86.7589	$86.76	$86.75	$86.80
Purchase #7	$69.27	6.551%	$73.8079	$73.81	$73.80	$73.80
7 purchase totals =	$1,001.03		$1,084.4405	$1,084.44	$1,084.40	$1,084.50