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	$35.59	4.364%	$37.1431	$37.14	$37.15	$37.10
Purchase #2	$176.59	3.252%	$182.3327	$182.33	$182.35	$182.30
Purchase #3	$29.86	9.121%	$32.5835	$32.58	$32.60	$32.60
Purchase #4	$185.97	3.721%	$192.8899	$192.89	$192.90	$192.90
Purchase #5	$170.44	11.371%	$189.8207	$189.82	$189.80	$189.80
Purchase #6	$165.73	9.449%	$181.3898	$181.39	$181.40	$181.40
Purchase #7	$93.75	3.224%	$96.7725	$96.77	$96.75	$96.80
7 purchase totals =	$857.93		$912.9322	$912.92	$912.95	$912.90