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	$120.40	9.200%	$131.4768	$131.48	$131.50	$131.50
Purchase #2	$182.99	7.251%	$196.2586	$196.26	$196.25	$196.30
Purchase #3	$195.88	4.789%	$205.2607	$205.26	$205.25	$205.30
Purchase #4	$110.69	3.272%	$114.3118	$114.31	$114.30	$114.30
Purchase #5	$189.67	10.502%	$209.5891	$209.59	$209.60	$209.60
Purchase #6	$135.41	4.190%	$141.0837	$141.08	$141.10	$141.10
Purchase #7	$17.71	8.629%	$19.2382	$19.24	$19.25	$19.20
7 purchase totals =	$952.75		$1,017.2189	$1,017.22	$1,017.25	$1,017.30