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	$185.37	10.711%	$205.225	$205.23	$205.25	$205.20
Purchase #2	$179.95	9.408%	$196.8797	$196.88	$196.90	$196.90
Purchase #3	$238.32	9.485%	$260.9247	$260.92	$260.90	$260.90
Purchase #4	$79.31	4.520%	$82.8948	$82.89	$82.90	$82.90
Purchase #5	$61.80	3.874%	$64.1941	$64.19	$64.20	$64.20
Purchase #6	$129.90	4.560%	$135.8234	$135.82	$135.80	$135.80
Purchase #7	$169.42	10.557%	$187.3057	$187.31	$187.30	$187.30
7 purchase totals =	$1,044.07		$1,133.2474	$1,133.24	$1,133.25	$1,133.20